Re: Margot, Margo, Margaux
Shorter and more convenient than Marguerite.
I don't mind it at all, but I wouldn't use it myself ... or not outside France anyway.
As for the spelling, the only one I can take seriously is Margot. I've been told that people started dropping the -t because other people started pronouncing it; which suggests a depressing view of humanity. As for Margaux, and her siblings Chardonnay, Sherry and Plonk, I can't take it seriously for the life of me, though it does give me some pleasure to imagine what the spelling-pronunciation brigade must make of it.