Quick question abous power-swap feats

[Kalbutt]

Hello

Can a character get multiple instances of a Power-Swap feat ?
For example to exchange multiple encounter powers with encounter powers of the second class (multiple Novice Power feat) ?

I can't see anything against this in the PHB. Would it be unbalanced ?

 

[Dalzig]

The rule is that you can not take the same feat twice (certain exceptions apply).