I have a designer doing his code inspections and wants the ability to cut text from the Crucible diff pane(window) so he can paste it into an external cross-referencing tool. Right now, clicking on the diff pane triggers the adding of a comment only.
I believe what you want can be achieved by clicking in the option File Diff as indicated in the following screenshot:
This will take you to the following screen, where you will be able to select the content:
In case you want to select only the content of multiple lines not including the other information shown by Crucible as Author and Line Number, you can uncheck these columns, letting only the content of the file.
I'm able to see the Fisheye->File Diff menu but only when my review content is defined by selecting changesets (i.e. svn revisions). If the review is based on a patch file which gets successfully anchored then there is no capability to "File Diff". Reviews based on patch files is an integral part of our code inspection process for small bug fixes where the designer will checkout the software code directly from main or a production branch. Therefore it can only be checked in once the code review is completed.