I'd played games that attempted similar things before – you know, short stories set entirely in a computer running some fictional OS.

but last seen online did it the best, in my opinion.

I think the fact that it's about the PAST really helps here: by NOT relying much on "present" IM conversations, instead leaving you mostly to read old chatlogs and investigate files, this game avoided the pitfall that similar games often fall in: letting dialog last long enough that it stops feeling like a conversation with a person, as the dialog tree becomes more and more obvious.

By avoiding this pitfall, this game managed to maintain immersion, which is CRUCIAL for a horror game.

I also love it that all the songs in LoseAmp are short, voice-and-guitar homemade folk-sounding tunes. It feels more personal, hinting at some past that the game doesn't go into: did the owner of the computer try being a composer? Or maybe they had a musician friend? Or maybe they stumbled upon a random stranger's songs on the internet and liked them enough to download them?

We-the-player can't really know; and we don't NEED to. If you were to find someone's old computer, investigate it as you might, the computer isn't going to teach you EVERYTHING about that person's life.

I mean, it's not like the person LITERALLY lives on inside the computer, is it?