As the subject states, I'd like to know if there's a way to block other registered users of this site. Specifically so I can't see a person's messages in forums. I'll even take anything that's like a chrome/firefox addon that's been jury-rigged to block messages of people here. I don't want to pick a fight with anyone, I just want to hide certain toxic persons so I can enjoy the forums better.

I don't believe so, no...

https://gist.github.com/Alice-Cheshire/dc5ebd1b7919cbd79aa648e2ebd96346/raw/9653380c6b3237f4e9529674871ac446259fe47e/dynastyblocker.user.js

If you have an extension such as TamperMonkey or GreaseMonkey installed then you could install this script and edit it to include the username of the person you don't want to see posts from. While it's probably not the case, however, I should warn you that using it to not see posts from site staff is inadvisable.