Please consider adding an option to reverse comment resolution, at least within a grace period. Comments get resolved by accident far too often. The “Resolve” link is placed more prominently than the “Comment” link, while being too visually similar.
In general I would also welcome an option to resolve individual comments. At least for me it would be perfectly fine to hide the resolve action in a comment’s context menu. Additionally there could be a context action “Resolve conversation” which would resolve all comments up to that point.