I'm going to hope this doesn't just add fuel to fires, but I feel like I might as well add to the discussion...
There's always going to be a connection between IC and OOC events and chat. The only thing that really changes is the extent, strength, and breadth of the connection. Most of the time, its relatively thin.
The problem is that if you openly admit, "my character is a pathological liar and an opportunistic backbiter," I, and probably everyone else in the RP community, will keep that in mind when dealing with you. My character, and probably everyone else's, will regard yours with caution. Anything they say will be filtered through the knowledge that it's probably a lie. This isn't to suggest we're purposefully trying to break the fourth wall. The problem is, if I/we know your character is capable and willing to betray me/us for their own gains, its going to be hard to say, discuss personal matters; I/we don't WANT my/our characters to get screwed.
Similarly, if you show yourself as a pathological liar and an opportunistic backbiter, the OOC side of the players you're dealing with goes on the defensive. Because they, like their characters, know you're willing to betray them for your own gains, and don't want to get screwed over; moreso, because that affects THEM, not their character.
So, there's the problem as I see it. We may not be our characters, but we certainly care enough about them not to let someone ICly or OOCly cut our throats or theirs.