I can repose the GMs answers on this yet again but...
The only reason they have said that is invalid for kicking someone is specifically to disrupt their completion of the duty (i.e. griefing).
For virtually any other reason, you can kick them. Point by point:
- no tank/dps stances definitely can kick
- no cleric stance definitely can kick
- using cleric stance definitely can kick
- no songs/turrets definitely can kick
- using songs/turrets (whether necessary or not) definitely can kick
- mixing glamour a stretch, but perceiving language as offensive is a valid reason, so theoretically...
- no melds definitely can kick
- having bad melds definitely can kick
- only aoeing definitely can kick
- only single target definitely can kick
- taking a piece of gear someone asked for can kick IF you don't try to do it before the loot window has closed. Trying to stop someone from rolling on loot after completing a fight can be classed as grief tactics.
- taking a piece of gear no one asked for a stretch, but see above. Theoretical reasoning could be needing on gear under your current slot's ilvl.
- being a job no one liked a stretch, but no job crystal at 30+ is valid. I, personally, would not risk a GM's ire for kicking a sprout, however.
- not doing mechanics definitely can kick
- not doing mechanics optimally definitely can kick
- doing the mechanics properly definitely can kick
Lastly, it's worth noting that a fair bit is up to GM discretion. If they feel you're being abusive (i.e. chain kicking people for some of the more obscure reasons listed), you might still find yourself in hot water. However, the more common ones (i.e. kicking someone for using or not using cleric, for doing an optimized/unoptimized rotation, or anything where casual and minmax playstyles are likely to clash) are likely the safest.
But the official response is playstyle differences are a valid reason to kick. Griefing people (by the GM's perception, not yours) is not a valid reason.