You know what it is for me? It's the fact that I read LJ as a Friends list, rather than individual people's blogs. So your professional stuff could pop up in between a post about one friend's cat hijinks and another friend's fanfic. And I like that about LJ, actually. I see it as a network/community of my friends, a way to keep all their blogs together. I don't necessarily want serious professional stuff mixed in.

I agree with you about the commenting and the ease of use, though. I think if I didn't have an LJ network and was just going to your webpage (which, yeah, probably would look more professional if it were gnomicutterance.livejournal.com...slashes always put me in mind of Geocities and therefore late-90s vanity webpage tackiness, but maybe that's just me), I wouldn't have the same bias.