I find it very annoying that TGraph::SetPoint(int,double,double) by hard simply deletes the member TGraph::fHistogram. Such, all titles and axis-titles are overwritten and have to be reset.
TGraph line 2131.
This avoids that one can simply initialize a TGraph and then set its points.
Furthermore, for the user it does not become clear, why TGraph::GetXaxis() returns different pointers before and after TGraph::SetPoint(), since one would naively expect that TGraph behaves similarly than TH1 and TAxis is a (direct) member of TGraph.
It would be more natural, to keep at least the title and axis-titles of the old histogram in some member like fOldHist, or even better have tow fHistograms: one for the cosmetics and one for the axis-ranges. Similarly, it is actually done in TGraph line 1514.
Thanks and cheers,