One reason to show old inlines even when they are marked "Done" is that the reviewer who added the inline may want to verify that it is actually done when they look at the updated diff.

So maybe it should be shown as a header with a possibility to show full comment? We sometimes encountered situation that there are too many comments in same place, but only few of them are relevant

I'm going to merge this into T7447, which has some ongoing discussion about this feature.

(Including discussion of the possibility of summarizing, hiding, etc., older inlines.)