In my opinion, if you blacklist someone, it is no longer your job to care about the situation. You willingly blocked someone away from yourself because you needed or wanted that separation. By continuing in engaging in the problem, even through the wall of blacklisting, you aren't letting go. You are keeping it alive.
I know nothing about the situation, but if you want to know what you can do, then that is a start. If they find other ways to contact you that is harassment and bypassing the blacklist in which case you notify a moderator or w/e. If it's outside of the site you blacklist them there.
Like I said, I don't know anything about the situation, but that kind of talk shouldn't be in a public forum like RT.