I almost always return a salute, unless the person who saluted me didn't deserve a return salute (they picked me or killed me in a gang 3 or 4 on 1.... yeh, I actually was all screwed up in a 1 v 3 once and a 4th guy came blowing through in a -4 Hog and picked me... then sent me a salute! I asked "WTF are you saluting me for?"
But for a good fight, yeh, I'll return a salute. To not do so makes ya look like a doushenozzle.
In the few instances where I salute someone who deserves one, and they don't return it, I'll send them another one a few minutes later, in case they missed the first one.
If they refuse to acknowledge the second one, depending on who it is, it may be time to openly mock them on 200.