[dllthomas]

One issue I was discussing with a colleague just the other day is that you cannot leave a comment on lines that are not "part of the diff" (changed or context), which is sometimes really useful for "see this thing over here".

[mattrick]

You definitely can comment on lines that haven't been changed. I don't think there's a way to comment on files that haven't been changed, though.

[codeapprove]

Actually you can’t comment on lines that haven’t been changed if they’re too far from the changed lines! It’s a weird limitation of GitHubs data model.

(source: that’s one of the features that people like most about the review tool I created, CodeApprove)

[dllthomas]

Annotations can be added by "checks" anywhere, though, I believe.

I like to use that to surface cross-references (annotating anchors whose references appear in changed or context lines, and references whose anchors do).

[dllthomas]

As the other commenter pointed out, only if they're close enough to a changed line. That's what I meant by "context" (borrowing terminology from diff, where you change the amount of it with -C).