I have wondered about this a long, long time. In Fontographer, BCPs have floating point values. So it appears to be allowable in PostScript. It came to an urgent point for me today when I opened up a PS font in Fontlab and a stem seemed distorted.
If I open this PS font in Fontographer, I get BCPs with x values of 326.7 and 324.7. In Fontlab, the values are 326 and 324 and the curve point is converted into a corner point. There is visible distortion of the stem in Fontlab. (There would be less if Fontlab rounded off more intelligently?)
I would like to learn more about this. Obviously PS fonts have floating point (at least to two decimal places, apparently) BCPs. How do interpreters deal with them?
Why does Fontlab round them off? Is there a way of subverting this behaviour? I am really worried about it. I am disturbed that Fog and Fontlab import PS fonts differently.