Comment 25 for bug 40412

Yes, bzr --merge3/--weave conflicts, so does xxdiff, and diff3 as you verified. kdiff3 doesn't. I'll see what kdiff3's author thinks about this. I believe that using more lines of context would give a safer merge (a conflict) in kdiff3. That probably relates to what you call "modifications on touching lines".
For sure, as far as I know, no tool will properly resolve a conflict where one side added "a++;" on line 10 and the other side rather added "a++;" on line 20. All tools will generate an automatic merge with both "a++" statements (which yields a wrong program). But in my testcase, as involved lines are so contiguous to each other... maybe something can be done... we will see.