Actually, for what it's worth, the FITS spec says that in such values trailing spaces are not significant, see page 7:
But they're not really relevant to numpy's situation, because as here you need to do elaborate de-quoting before they can go into a data structure. What I was wondering was whether people have data lying around with fixed-width fields where the strings are space-padded, so that numpy needs to support that.

I would say whether to strip space-padded strings should be the reader's problem, not numpy's