Don't hide comments as against 'previous versions' unless that file was changed

Scenario:

• Pull Request has changes to two files A and B
• reviewer puts a comment on file A
• developer commits and pushes an update to file B
• now the Pull Request hides the comment on file A. It can only be seen when clicking the link for comments on previous versions of this file.

This seems unnecessary: the file A hasn't changed so the comment isn't on a previous version. Instead the comment should continue to be displayed in the main area unless that file has been changed. Even better, keep the comment there unless the line that was commented on has been changed (or perhaps lines near to that line are changed).