I've found this causes a bug in the latest release of XenForo 2.2.2. When a member tries to 'Report' a bad post by clicking the link you end up getting this message no matter what you enter:
The issue went away when I disabled this addon.
I've got an unusual bug with the latest release of XenForo, which has been spotted by both users of my forum and now myself, but it's a bit random. On PHP 7.4 and MySQL 5.7. Sometimes when a member goes to 'Report' a post they find that, no matter what they put in the 'Report Reason' box, it...
xenforo.com
UPDATE: I forgot to add that the "please enter a title.." message seems a bit random. On some posts the 'Report' feature works fine, but on others you get the above. I haven't established a trend yet.