Can I just say, and I'm just being honest...

[Excited Penguin]

CIJS: It's good to be back! How long was I gone? Feels like forever. I didn't like it.

My username is covered in marmalade. Fair enough.

I always find it amusing when someone says, halfway through a conversation, "To be honest with you...." I wonder if this is an admission to lying up to that point.

No, it's not an admission to lying, it's to evidentiate that what is going to be said is going to be delicate for the other to hear, in order to attenuate any negative reaction to it. That or something to that effect, if you're talking about other people, except then it's more about extirpating guilt over being a gossip than softening blows. At least this is how I see this phrase being used. Of course it's sometimes used as nothing more than a simple prop for what's about to be said. Theatrics of that sort can play a role in conversation as well.