Well, that's nice and all, but blacklisting =/= reporting.
I blacklist them too to be able to check if they got deleted.
Lately, reported characters who send RMT tells get deleted rather quick. If by SE or by themself, I don't know.
Something I do know, is that bots and hackers don't get penalized at all.
I report every bot or teleport/speed hack character I come across. So far it's about 30 over the past ~10 weeks and none of them are gone.
Regarding the OP post, I came across something similar just recently in Coerthas at the Merchant & Mender in the Observatorium.
Suddenly a character with a strange name like "Ychrsot Grusnat" (just an example) would pop, stand there for about 10-15 seconds and then vanish again.
A few minutes later another character with strange name pops and depops again.
I noticed 4 of them, all lvl50 archers (not bards) with gear around lvl40-45 (all got the same gear), same race, character model and looks.
Checked them on the Lodestone, no mounts, no pets, no other classes, no faction, no free company.
One more thing I noticed is that they were in party as soon as they spawned and at least 2 of them were party leaders.
When they vanished character search couldn't find them anymore.
Reported all of them with a clear description but nothing happened, as usual.