right now, AFAIK, when attributes of a message like read/unread, 'starred/unstarred', 'forwarded', 'replied', or tags change, gloda reindexes the whole message (although I think we don't reindex the full-text. that feels like it could be optimized, with less time spent 'dirty'. (to say nothing of 'move to archive', which is likely much more complicated)

Already have a bug on this, although given how fast indexing is, I'm somewhat reluctant to pursue this since it seems likely to shoot reasonable extensions in the foot.