/t and /m in WvW
One of them is a slightly different color and has a different name. That is all.
Both do the same thing. There’s no cross-map chat (between EBG and the borderlands) and there’s no communication with the opposing team.
I’m not sure why they kept both, because I remember them saying they would remove one of the two. I do like it though, makes it easier to announce something important in bold red.