It's a joke that probably made a lot more sense in the 90s. Back then people would use ™ everywhere, in logos, whenever certain brands were mentioned, etc.
In my opinion it fits the general humor of the game perfectly, but I can definitely see how it would could be annoying.
I was nineteen when the game came out and I got that joke. It's an important part of selling the broader joke that the world of Monkey Island is probably more of a pirate-themed amusement park, owned by a faceless corporation, than it is an actual world.
Just to weight in here, I completely got that also. I probably would have played somewhere in the mid-90s, when I was ~11-13.
As far as I knew, forums didn't even exist at the time (Of course, there probably were forums, and of course mailing lists and usenet were around before that, but I didn't know about them). It really just fit the humour style of the game, not taking itself too seriously. To be honest, it was far from the funniest joke in the game.
In my opinion it fits the general humor of the game perfectly, but I can definitely see how it would could be annoying.