4192: review comments are easily missed on the diff view


What version are you running?


What's the URL of the page this enhancement relates to, if any?


Describe the enhancement and the motivation for it.

when viewing a diff review comments appear only as a tiny number in the left margin. this makes them easy to overlook, especially when viewing side-by-side diffs where your focus is on the right column.

it's especially problematic for users who are new to review board, as pretty well all other review systems show the comments inline, in a way that is impossible to miss. i understand that this approach isn't one that review board prefers.

for mozilla i've made a change that just adds a dotted line across the entire diff page. this has a number of advantages:
- it draws attention to the existence and location of review comments
- it's non-obtrusive; code isn't broken by comments, and the colour used is faint enough to avoid being distracting

see attached screenshot.

i'm happy to develop a patch to add this to review board should this approach be green lit.