As the title say.
Got a player pull this doozy
His character used a move action to move 6, then another move action to move 2, and hid as part of the second move. Does he suffer the -5 penalty to stealth or not?
Verrrry good question.
The answer, RAW, is kinda complicated.
Opposed Check: Stealth vs. passive Perception. If multiple enemies are present, your Stealth check is opposed by each enemy’s passive Perception check. If you move more than 2 squares during the move action, you take a –5 penalty to the Stealth check. If you run, the penalty is –10.
The entry that is in the PHB is pretty much the first 4e errata ever, so can't go by that--the current version mentions that the penalty occurs based on that action's movement.
So... if that second action involves more than 2 squares of movement, then you get the penalty.
In your example, you have a player 'move' 6 then 'move' 2. But one thing I want to clear up is that there is no such thing as a 'move' as an action you can take. 'Move' is a general term, there are specific terms for each action. The accurate term for that move is 'walk.'
This is actually important.
Let's say you run 6 and then walk 2. During the action you stealthed on, you moved 2 squares only, so do not get the penalty to your roll.
Another example: You walked 6, and then shifted 2 (using a power, or you just get a bonus to shifts). Again, you don't get the penalty to your roll.
But what happens if you walk 6, then walk 2? Well, you're taking the same move action twice in a row, which transforms them into a single double move. That means on that action you stealthed with, you've moved 8 and therefore cannot stealth.
However... and this is where it gets more complicated... this only occurs if you do both moves in a row. If you walk 6, reload your crossbow, then walk 2, you've broken the two move actions up with a minor action, thusly you are -not- taking a double move, and you can stealth without penalty.
tl;dr:
If you're taking two different move actions, or a minor action between those two move actions, you do not get the penalty. If you take the same move action twice in a row, you do get the penalty.
Personally tho... as a DM I'd probably just make my own decision on it and damn this highly technical corner case rules interpretation.