Provide line by line requirement compare
Provide line by line requirement compare highlighting differences
Available in Caliber 11.4 (12/1/2014).
you can probably find a web tool and insert it into the custom tools. I use free tool called Diff checker which is adequate.
Ian Pletcher commented
Ideally, this should work like the Word track changes functionality - i.e. you can view a single version of the requirement with all changes since a specified version of the requirement highlighted as insertions, deletions or moves.