The blacklist system should be revamped that I agree. This situation however I don't even think is worth reporting. Just seems like a harmless lonely person with social issues.
If someone is actually stalking you in game though, my advice is to try to change your perspective. Instead of being like "oh god this person again" I think like "haha this idiot is back to waste his time". If you don't give them any attention you are literally just wasting their time.
That after reporting if needed of course.