Have a number of read only users, that appear to all be setup the same way, though one of the users is somehow being logged as the user for the last-modified date on the contact. Again, checked the user configs and as far as I am able to tell, they're exactly the same except for the user related data such as Name, Alias, Email, Username, Nickname, etc.
Any suggestions about how to track down both what Salesforce believes was changed, and why this user, and only this user is being logged to the last-modified date on contacts?
UPDATE: Finally, after clicking around, and around, I found something, and in fact, appears to be something that the answer below might have suggested as the source; though indirectly, sense it appears to be code from the NPSP that's the source of the issue. Selected the answer below as the answer, and posted a new question here: How to find/stop/disable Apex Jobs that a read-only user has activated