Dear All,
Ok - I am outing myself as a being NOT a power-user like everyone else here by asking following question:
Why Markdown? What is the advantage of Markdown, why would I not use a wordprocessor which is showing bold as bold, or italic as italic? Isn‘t it more complicated to type Markdown and to get into it from the start?
Everybody is so into it that I am sure I am missing something and I hate missing things 
Thanks for the enlightenment!
Markdown is like plain text - it’s portable and easily converted to other things. If I write in Word then I need the other person to have Word or something that can open a Word document for them to see it, but every operating system can read plain text files. Rich text can be saved in many ways, and the which is the tricky part 
Also, for us programmers it’s often supported in IDEs
I think one of the benefits is transmogrification. You can take plain text written as Markdown and quickly and automatically have it convert to HTML, PDF, .docx, ePub, etc. It is a great baseline format that can then be morphed into whatever format is needed for the publishing purpose.
To add to what others have shared, when I write in a traditional word processor (e.g. Pages) I find that I inevitably get a little (or a lot) fiddly with fonts and other styling elements.
With Markdown the focus is on the words and, if I’m using an app like Bear or Ulysses, the text looks very presentable without me having to do any additional work.
p.s. If you want to get some practice with Markdown, it’s supported on this forum.
Others have already mentioned it’s plain text nature, ease of transformation into other formats, and lack of fiddliness. I also really like that it’s all text, no taking my hands off the keyboard, no guessing at what invisible options are producing the formatting that I’m seeing in a word processor.
It also provides very simple support for more advanced features: links, images, and, with MultiMarkdown, footnotes and tables.
I’ve fallen in love with Markdown too. But it’s not a complete solution. Quite a lot depends on where you want your text to end up.
As a lawyer, much of what I write ends up in Word. I’m a power-user of Word. I make full use of styles and rely on them to get my writing into the proper format quickly. If there were a way to reliably convert markdown (or, ideally, multi-markdown) into a purely styled Word document, I’d be in heaven. But there’s not. I haven’t been able to get Pandoc to do it right. Ulysses’s Word export is rather wonky (it will style headings, for example, but footnotes get direct formatting rather than a style).
In many cases, much as I hate to admit it, I’m better off just using Word itself. Perhaps if I ever become a LaTeX style ninja, I can skip Word. But unitl that day comes, I’ll keep using markdown for all my notes and early drafts, and Word to produce finished documents.
I felt the same way. For a long time, I didn’t get what the big deal was. I write for a living, and I’ve never been in a situation in which using Markdown would make my job, or my colleagues’ jobs, any easier to do. (And I’ve asked.)
I didn’t let that dissuade me from eventually learning Markdown, and I don’t think it should dissuade you from learning it, either. It may come in handy some day. It’s certainly not difficult to learn. For me, the only difficulty with Markdown is in making it applicable to what I’m doing. I could write everything in Markdown, but I’d still have to find a way to get that copy into Word so that other people who don’t know or don’t need Markdown (i.e., everyone I work with) can work on the document.
About a year ago, I made the decision to use only Markdown when writing anything in Devonthink Pro, just to make sure I’m adept at using Markdown should the day I need to use it ever arrive.
Recall that Markdown had its origins in plain text email conventions - so for many users it’s a matter of going back to or continuing to add markup as we have for many years, just with some stricter rules about syntax and a lot more opportunities for post-processing.
Very important point. Anything beyond basic formatting is difficult to do in plain text / markdown. Tables are where markdown fails for me. I write a lot of documents that require tables and never attempt them with markdown**. Creating a table with markdown feels metaphorically like I’m writing a program just to make the table appear; versus with Pages or Word I just drag out the table and fill it in.
Like anything else, being adept at picking the right tool for the job is the key skill to develop.
**Technically, tables belong to MultiMarkdown and other non-Gruber Markdown flavors.
Because you find it useful. …fun.
Not a smart aleck remark… For me It took hours of exploration with markdown friendly apps such as Ulysses or Drafts. I also made WordPress’s editor markdown friendly using a Jetpack plugin.
That said, I do not use markdown to build tables or APA style documents. Fortunately my formatting demands are straight forward. If not I use additional tools.
I use it to easily post to my blog from something quick and easy like Drafts or Ulysses. I don’t do tons of formatting with it, but it makes it easy to use automation for things like inserting links and referencing images.
I think I started using it when I was still using Squarespace and the interface was awful on iOS. Pasting in markdown let me bypass their terrible, glitchy, desktop-first, back end.
We have a database at work that only supports plain text input, so for me, it’s an easy way to cheat, and it’s not too weird for my staff…
Where markdown supported writing apps fall down for me is printing. It seems like markdown was really meant for conversion to web text. So to find markdown focused apps that give you better printing options is tough. It’s just not written into the syntax. So fairly basic things like page breaks, margins, etc. are not supported. I usually have to cut and paste into Word for even basic printouts that are longer than one page!
I write for the web and markdown is less typing than HTML. [link](www.url.com) instead of <a href="http://www.url.com">link</a> and so forth. Easy to convert when I’m done.
I like markdown for short to medium writing projects. I can create headers and links with minimal fuss. Using Marked 2 I can get the text into email, printed or rtf. I do not have to fool around with font choices and style menus. As for italics and bold- markdown has very little advantage over a word processor. I would think larger - (semantic) section headings, footnotes, links etc… with just plain portable text(use any editor of your choice). Only LaTex could give you more control(but a much steeper learning curve).
So, being in the same camp as the OP… where do I go for the best intro to Markdown? Since I just started using Drafts I guess I’ll have a good reason for learning this stuff if I want to count as a power user. 
Otherwise you won’t get your badge and gun emoji
I learned Markdown by using Ulysses.
Ulysses has a tear-out menu that creates a floating palette of all the Markdown syntax. I place place it on the side of the main Ulysses window and would refer to it when I needed to remember some Markdown syntax. I started off with headings, bold, italic,. After a while, you’ll get the hang of it and won’t need it as much.
I write in markdown without worrying about formatting. I can use Command-B for bold and Command-I for italics.
I can also open a live preview window and see the changes as I need it.
I still don’t like making tables in any Markdown editors. I end up making them in Pages and export a PDF of that to use in Ulysses.
Wow - thanks for all the answers so far!
Let me summarise of what I understood:
So I looked at the Markdown options and probably I have not seen it all but when it comes to text with tables, lots of pictures, different fonts, footnotes, etc. it seems to become quite complicated sometimes even lacking capabilities (can I move images around in the text, have the ext wrapping etc. ?) … what buys me in though is the plain text argument and the sharing fact.
I think I have to follow @RosemaryOrchard advice and get the book from the one and only @MacSparky - after all, I do not want people to call me a rookie
Plus, it’s like our very own secret handshake…shhh…