It's wit hall moves. The more times you do a single move consecutively it does less damage, by a factor decreasing each time until it just abotu levels out to a minimum damage.
So to keep damage done up, you should not constantly bitch one move. If you use any other move to break the "chain" of you bitching that one move, the next time you use that one move it will be back at full power.
You should be using more than one move anyway to keep your predictability down. For people who constantly mix up their strategy so their opponent can't read their moves, the "stale moves rule" as you call it has next to no effect. I only use projectiles for a pressure game so I'm happy.
QUOTE(notnarb @ Apr 20 2008, 11:28 PM) Yes it appliess to all moves, but, apparently, stale moves don't just count consecutively, but rather for the past 10-ish moves you have done. This is easiest explained through an example
f-smash, ftilt - both do full damage
f-smash, f-smash - the second fsmash does a little less damage and knockback then the first
f-smash, f-tilt, f-smash - the second f-smash does as much damage as it did in the second scenario
f-smash, f-smash, f-smash - the second does less then the first and the third less then the second
It should also be noted that a percent here and there isn't going to be a world of difference, however, because the same %loss of damage is also applied to knock back (19% instead of 20%, 5% less knockback) therefore, you should use finishing moves sparingly