Two bugs related to threads - invisible, impossible to remove mentions and ability to search messages in private channels.

Hello, I'm Matt. I've found a bug recently and made a bug report for it, but Discord Support didn't think much of it and I do think it's an important one that should be fixed.
Anyways, it's possible to ping everyone in a server and have them unable to get rid of the mention indicator. It's also possible for those people to search *any* messages in that thread, even if it is not accessible by them.
Please, if you are a Discord Employee, contact me and I'll let you know the details. Sorry if it's a known bug.
Proof for the impossible to remove mention: