I think I have 5. 3 because they were non-stop spamming sound effects in a Frontlines I was in, one because they were excessively hostile towards me in whispers, and the last one I blocked back in ARR and can't remember why. I honestly don't meet very many toxic players in this game that annoy me to the point that I have to blacklist them.

It's pointless to keep RMT spam bots blacklisted as their accounts are banned within a couple hours and then a new one is created. If you seriously need more room to blacklist people, clear out those first.