if too extreme farming an instance will blizz ban a/c?
since the gold are use for in game not selling

As long as you dont use exploits or bots to farm or there is any real life transaction to buy/sell gold. i dont think Blizz will ban.

Furthermore u cant really go extreme farming on an instance..theres a limit on how many times u can reset the instance

Bliz only will ban your account if they suspect/find out you are actually selling gold. normally this is detected through the sending of stupidly huge amounts of gold to another account.

so unless you aren't sending 100g to several separate accounts, you're safe.

[WTS]? What's the [WTS] for??

i think he meant [WTA]