You are right.
W is derived from "warai (笑い)” in Japanese and we have lots of idioms made of it.
For example "cyousyou (嘲笑)” is one of them and contains a meaning of insult
Some people tend to say bad things about others or make fun of others because of their anonymity.
I think " ha ha ha" is similar to " kousyou (哄笑), which means laughing with your mouth open