I’ve had this happen when trying to use a password longer than 60 characters. I could set it just fine through registration or password reset, but I could not log in with it. Limiting the length of my password to 60 characters resolved the issue.

XPrivacyLua is no longer maintained YFI. It still seems to work just fine for now, but that probably won’t last. I’ve not found a good replacement for it yet.

They would show for others on your instance, but not for people on other instances, so each instance will have a separate downvote counter.