Long comments squeeze diff towards unreadability

Summary

When adding comments with long lines to diffs, the diff becomes unreadable.

Steps to reproduce

• add a comment with a long line to any diff

Expected behavior

A certain amount of space is reserved for each side of the diff (40%?).

Screenshot

https://gitlab.com/winniehell/reproduction-area/commit/9101e66f5761929002956e0f2dd65d7f8643903d#note_13649380

Possible fixes

add max-width: 40%

Also the comment can't be remove because the buttons are hidden.

Reassigned to @iamphill

mentioned in commit a027740f

mentioned in merge request !6309 (merged)

Status changed to closed by merge request !6309 (merged)

Mentioned in commit a027740f

Mentioned in commit e15c8e8f

Mentioned in commit 7706164e

mentioned in merge request !14785