Mistwell
Crusty Old Meatwad
That remains to be seen. Like many things, we won't know until we try it!
I'm of the opinion that it will increase use of the rep system. And that posrep is one of those little things that really makes your day (in a minor way). So the more of that, the better; getting posrep makes people happy. Happy people are nice people.
I think it is likely that if you make all rep comments visible, with no way to hide it, that you will not get a net result of happier and nicer people. Instead, I think rep comments will be used as a tool to fan the flames of arguments and competition, and will become more of a headache for your mods.
It's already happening. Already in this thread you had people jokingly soliciting XP. Do you honestly think, given your user base is fans of a set of games, that it won't foster competition (and sometimes not in a good way)?