"<p>Tag type cannot be changed: Permission Denied when trying to change tag "hariet_(mario)" to type character</p>"

That's the error that pops up when I try to change hariet (mario) from a general tag to a character tag. Hariet is definitely a character, so it shouldn't stay like that. Hopefully this isn't just an issue on my end, but it looks the same on multiple browsers.

Nah it's not an error, it's because the tag has more than 100 posts. You'll need to contact a mod to fix it; I've done it before with other character tags that were mislabeled as general.