Stealth and flanking

[Audrik]

I don't have the books in front of me at the moment, but I was just thinking ...

It seems that combat advantage from flanking comes because the target knows it's flanked and has to defend two directions at once. If a rogue is hidden, wizard is invisible, etc ... Obviously he can GAIN combat advantage, but can he also PROVIDE it?

 

[yu gnomi]

By the rules, yes.

It can easily be explained by the fact that invisible PCs and monsters still make noise when fighting for their lives. They also occasionally stab things while invisible. So the opponent is likely to suspect that there is an enemy flanking him, although it won't know exactly where that enemy is.