[Deckard]

I'd do one of two things.

Either come clean about how you stumbled on his blog, acknowledge the awkwardness of the situation, but just be casual about it, laugh it off, and try best to carry on as normal. Hopefully the period of freakedoutedness will be shortlived. If it's not, well, you tried.

So either that - or back away completely. Cut your losses. Let the friendship dwindle. That's the equivalent of turning around and walking back the way you came.

Which you choose depends on how much you value the new friendship's potential versus how mortified you (and your 'almost'-ex, and perhaps to a lesser extent, the friend) would feel about the whole thing.

Weighing up one versus the other (and not being able to fully predict their reactions) is the difficult thing.

What I wouldn't do, though, is prolong the anonymity. I mean, you can have anonymous friendships on the internet - we all have them to varying degrees - but in your case, there's a secret that you're carrying around which adds a layer of duplicity to the interactions, and the longer you keep that secret, the more deceitful it will seem if and when you do decide to come clean. In other words, trying to pursue and develop a meaningful friendship on this basis is, I think, a dead end.