I think a browse player page that only shows players that you haven't (or can't) attacked yet would be very interesting and take some of the peicemeal time consumption out of leveling up. Therefore, lowering the huge percentage of players who would not be considered "low" level despite the hours they put in to change that. It would also help the higher level characters maintain a steadier growth as well by making it so they don't have to guess who they can and cannot attack. a**uming of course they are not smart enough to figure that out by themselves.
Hope that makes sense. Also hope that it hasn't been suggest already.
The Player Browser is cached, so I can't hide players from the list on that basis, I'm afraid.
However, the Attack icon only shows on players are can attack. It does not check the attack log, however.