Personally....I think posting "tent" at best means:
"I'm really interested in coming, but cannot confirm at this moment"
At worst it means:
"I may or may not attend...don't count on me...posting this is useless re. the game in anyway"
Either way, it's not very helpful for the organizer/host to know if guys are tent. Pretty much only "IN"s count, and even then guys flake (i.e. don't show up and give no notice that they're bailing on the game).
The host needs to know if enough guys are going to show so that he can run the game or not...if he'll have to rebalance the teams...etc.... Tent's are not helpfull for that.
My advice would be...unless you can commit to the game, don't bother posting anything.