I remember when it worked for the most part when Wipeout HD came out. I do agree it would be distracting to try to talk/trash talk while racing, especially during a phantom race, but I would enjoy talking/trash talking amongst friends via headsets. If they ever decide to fix the talking issue, I hope they change the way you have to talk during a game. For this there are several options:
A) No buttons held required, talking is always on.
B) Have a button to toggle talking. ( Press L3, or a different button of your choice via control options to enable/disable talking) Punisher No Mercy does this very well with Down and Right on the D-Pad. Down toggles Mic, and Right toggles Headset. Back to Wipeout HD. If I recall correctly, R3 isn't used for anything, so maybe you have L3 toggle Mic, and R3 toggle Headset. These settings could be changed to your own preferences. They work for me since I race with D-Pad, hehe. Or just keep things simple and have only L3 toggle chat, and if you are getting annoying by someone, just mute them or take off your headset.
C) Keep it where you have to hold down a button. This is the least desired option in my opinion, because it can be distracting and mess up the whole race. I guess it could be a blessing for some and a curse. (Imagine a guy trying to trash talk you and then they crash because they're holding down L3 LOL) And if anyone is concerned about annoying/offensive people, put in a Mute option, maybe even an abuse report button, but that may be taking it to far. But yeah, with SL at hard work at the moment, the recent release of 2 patches, and Fury, I am very satisfied and respect them very much. I'm just saying if they fixed the chat system, (via option A or B), which was included from start, this game would be perfect.