I sometimes encounter the poster who reminds me of other poster with different username. Normally those are the ones who seems to have very concrete/fixed view, not in the bad/malicious way. I get tempted to ask if they used to be XXX, but haven't done so.
Is this, asking other poster if they used to be XXX, considered unacceptable on MN?
Sorry for silly question, but I really don't want to cross the lines without knowing.