For the few people that would use it for good there are just too many people that would use it to taunt, greef, badmouth, harass, scorn, humiliate, etc . It would be non stop shit talking with every pvp encounter degenerating into endless ragefull hate rants.
You can always head to Discord. Also Guild chat will be global I believe. Yes, it's part of the design that people can't just communicate across miles, to encourage people to interact locally, use voice chat etc in game.
the fact that we have discord now goes to show why I think a global chat in game would be nice I can just chat and hang with ppl ingame all the negatives of a global chat will exist anyway because we have discord anyway
Discord can be useless too... Their New Player Questions is bloody 1 hour cooldown and their normal chat is like 5min+ Sure it's more busy today, but it will be busy at launch, etc as well. They need more channels and more moderators to help keep things going without punishing new players who can't even ask for help.
Also the Discord at times is full of racism and politics... No one seems to care it just happens people ping mods hours later I scroll up... I'm thinking the best thing to do is find a group of players to play with and interact with them and their own private discord. The forums at least seem helpful.