I don’t tend to check beforehand, but don’t think it would spoil my enjoyment whatsoever if I did. Just looked at the past couple of Nick Cave shows prior to seeing him tomorrow to get an idea for example, and if anything it’s probably just made me more excited.
CAVEAT: if it’s a situation where timings with a babysitter are tight I have been known to research what the final encore song will be in order to start making a move to the exit preemptively.
To answer the OP - I have also on occasion made edits to setlist.com where there’s stuff that I know is wrong (usually only minor stuff where it’s credited to the wrong album or isn’t flagged as a cover version or similar). I like setlist.com so figure why not give a little bit of love back