When typing a link in Markdown and mentioning a user in the link text, things go a bit wrong. Imagine I type this:
[This link was made by @sanderdatema using Markdown](http://theurl.ext)
This will result in:
Notice the text ‘using Markdown’ is no longer part of the link text. That’s because there’s a link to the mentioned user as well.
So, this is a rare case of course, but still, it’s a bit of a bug.