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As I said previously, the only reason for the change was get all the docstring signature lines for builtins, after they were changed from 1 to many. I was not thrilled with having to do this. However, I felt that just presenting the arbitrary first of many lines was (and would be) a bug.
For 3.4+, this is a temporary measure until Argument Clinic is applied to enough builtins to make it sensible to switch calltips to using str(inspect.signature). See #19903. When A.C. is applied to a function, the signature is no longer in the docstring, which instead starts with 'Returns (or whatever) just as for python-coded functions.
Since A.C. and #19903 do not apply to 2.7, feel free to develop a more permanent alternative for 2.7. Perhaps just say <expand multiple line signature> and have a click on that line do the expansion instead of dismissing the box.
If you do, I can check whether the A.C conversion has been slow enough to make temporary application to 3.4 worthwhile, or if *really* slow, to 3.5. The click idea, while still needed, might be combined with using .signature, but I have to recheck its current behavior.