Collapsed lines in diffs are too low-contrast
When reviewing code changes, collapsed lines are very low-contrast relative to the colors around them. It's a little too subtle and makes it much more difficult to notice when lines are being hidden.
GitLab is also collapsing down single lines of code. Because of our style conventions, it seems to be frequently targeting one-line method names. This hides the relevant method name and makes the code appear to belong to a different method. Seems like only groups of 2-3+ lines should be collapsed.
The inline comments also make it very hard to transition between reading the code and reading comments. Comments off to the side on wide displays would be very much appreciated.
I'd also like to note that while I have good vision, there are plenty of engineers that have vision limitations. I can't imagine how hard these issues make it for them to use what is otherwise a very good tool.