- Edited
"Updated" works, but sounds a bit jargonish. "Answered" is good too, except it implies that the OP is a question. But I'm wondering what the objective is. In terms of screen real estate, there isn't much difference:
Last reply
Updated
... About half an em is all (if even that). So perhaps the issue is not just length, but the fact that there's no verb? If that's the case, then I think something like this would work:
Updated by Toby 2 hours ago
It does seem a bit more natural to have the time at the end. (You can't do that with "Last reply" because then it sounds like we're talking about the last of several replies made by Toby.) And you could change the "Started by" string to match.
Of course then the username is a bit closer to the avatar...