Why not just leave them uncollapsed and allow one to mark them as resolved when the change is actually resolved. The other problem is that it's difficult to see what actually changed when a line is marked out of date without having to scan through the entire updated diff and then jump back and forth between the diff and conversation view.

Collapsing them by default makes it difficult to find the comment by scanning. If they were uncollapsed until I marked them as resolved, then I could at least use the find feature in the browser and search for my username to find my comments.

Except that if the overall diff line I choose to comment on about the commit message changes in some way, then the comment is collapsed, which makes it difficult to keep track of what needs to change.

> since by the time the PR is done the commit msgs are pretty much not changeable, except for the last one

They can be changed via a git rebase.