Diff application with posibility to input text manually Is there some application, which allows you to open just 2 blank panes and paste there text manually, so I don't have to save them into files before comparing them and I can edit files directly in panes?

And I would like comparison like Kaleidoscope or something similar, which can hilight what's different in particular line, not just hilight that this line was changed and I have to spot the difference manually

Meld for Linux is capable of doing so, but I didn't find any native apps for Mac
If you can't find an alternative to meld, consider installing it via MacPorts:

sudo port install meld