Depends on my role, but I play tank most often so I'll go by that.

By default healer gets my comm, but that can change depending on a few factors. If the healer is a healbot and doesn't contribute to dps, they don't get it. If they let me die at any point they've probably lost it as well unless it's a sheer party-wide mess-up. If either of these happened usually the dps who I think did the most damage/had less "afk" looking time gets it

But one thing that will always get a dps my comm, is aoe lb'ing a wall to wall pull. I see it happen so little, if they do it without me asking they're commed, I don't care about anything else