I would say if you like someone's post, and it resonates with you, and it's worthy of an applaud, then do so.

It might make the person feel just that little bit better about themselves. Don't worry so much about how often you do it. After all, there are a lot of wonderful people here, who regularly contribute a whole heap of fantastic input. No reason you can't show your appreciation for whatever you find which personally stands out to you, hon.

I highly doubt you would get banned for showing more than one person how much their posts meant to you.
Applauding someone for putting down someone else, or taking a side-swipe at another member... well, that's something different. But as a general rule of thumb, if you genuinely enjoyed someone's post and feel it's worthy of an applaud, then applaud away.

There are folks who use the reputation system more than others. I use it myself when I'm in the mood, or when something speaks to me. I don't think a post has to be something truly spectacular and crafted in a manner the finest wordsmiths would go into paroxysms of joy over. Sometimes it can just be a way of saying "I like what you wrote and agree with you", without having to make a post saying such.