I will sometimes come across a listing on the MLS where the address appears to be intentionally modified to skew the days on market. Should I report those instances?

Yes, please use the Report Violations Tool to notify MLS Staff of an inaccurate address. Staff will adjust the address so that the history properly shows all listings at that address and so that the days on market are accurate. Your name will not be disclosed as part of this process. This can sometimes be a simple error, but other times it is intentional to make the listing appears as if it had zero days on market at the time of entry. If it appears to be the latter, the GRAR Grievance Committee will investigate.