Maybe it's there to remind him how NOT to go wrong with his next relationship. Or perhaps, as some have already pointed out, he simply wears it because it is a nice ring (you've said so yourself). There could be all sorts of reasons why he's continuing to wear his wedding ring. In which case you could be pleased that he's wearing it. If it indeed was a NASTY divorce I doubt he's wearing it to remind him of his ex-wife - or perhaps it's there to remind of how she was before the divorce so he doesn't get mired down in feelings of hatred and bitterness.
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