It would be better to indicate last activity was a question deletion.

I've just edited the top of the question to change it from a link to a closed GitHub issue to a more general GitHub issue. That one mentions the possibility of indicating there was an answer deletion on the question. It currently states this decision could go either way, so it might be worth putting your reasons into an answer here or a comment on the GitHub issue.

(Note that question deletion is harder to indicate, and isn't mentioned in the GitHub issue as intended work - that might need raising separately if you consider it needed. Answer deletion can be shown because the question still exists to put a message on.)

Sorry, I meant deletion of an answer to an existing question.

Ah I see. The recent comments on that GitHub issue suggest that answer deletion will be labelled as such, as you recommend. I've edited this Meta post to make it clearer that this one concerns the grey circle indicators and question deletion rather than answer deletion, and I've added a new GitHub issue for that as it's a separate problem (and linked to it from the top of this Meta post).