hashtags in urls are detected as tags
If there’s a url with a # in it, then it’s detected as a tag by the tag plugin
I can’t reproduce. Please be more specific and post an example if you can.
It stopped reproducing for me too somehow 
#s used to show up as a tag before though from this url
https://mail.google.com/mail/u/0/#search/enjoy+more+/ABCDEFgA
How do I close an issue…
@WhiteNoise I came here to report this exact same thing. #s inside URLs and internal links is being recognised as a tag.
(v0.8.8, macOS Catalina)
Since this post is already in the graveyard, shall I create a new bug report?
UPDATE:
Well, it’s partially sorted out. I did indeed have a #s inside one of the notes, and so it made sense that the tag appeared in the tags panel.
The confusing part is all those incorrect matches in the search that’s invoked by clicking the tag. They shouldn’t be there, should they? The search queries generated by tags should show tags only.
No need, I open the bug again. I have a better undestand of it now.
This will be fixed in 0.8.9+ when we move complitely to searching tag with tag:#tagname