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I noticed that the space between the left parenthesis - ( - and "f" in Kepler Std looks more like a blank space: "( f)" instead of "(f)".
I think this might be some bad kerning in the font itself, and the only solution I've found is through XeLaTeX (which is the typesetting software I use, anyway):
The issue, however, seems a little bit annoying coming from such a large family which looks pretty nice both on paper and on screen, and for such a widely used letter pairing -- I use (figure X) all the time.