If someone uses hashtags in posts or comments, they are interpreted as headline. Here’s a screenshot and a link of an example:
My suggestion would be to only parse it as a headline, if between the # and the next word is a whitespace. I’ve seen it that way in other markdown parsers and I think that works well.
Edit: Typo
I think this is fixed in the latest version already
That fix was to post titles only. Unfortunately that fix will not affect the issue reported here.