Quote Originally Posted by Jijifli View Post
If anything this is an issue that's, at least, bug related.

The only ways to blacklist a person at the moment is to have been in a party with them very recently, see their chat (and sometimes the button vanishes for whatever reason), or to personally target them yourself and do /blacklist add <t> instead of their name.
I don't think it's a bug as much as an effect of the recent changes. They are likely going to be adjusting it in the expansion release if anything