[Game_Ender]

Have you tried Phabricator? It tracks completion status of comments on a review. Letting you easily find the un-finished ones. Comments can also apply to single or multi-line sections of the file, and they stay present even as the patch itself is updated in response to comments.

[fyi1183]

Phabricator is decent in many ways, but it's terrible at handling patch series. Most people don't seem to be aware of the feature at all, and it's not integrated at all into tools like arcanist.