I have never had this issue, concerning "counterfeit" notes.
I have had, on a couple of occasions, I bank teller raise up their nose at me because of 'defacing' the notes, and that they are now considered "mutilated" bills and are sent out to be destroyed.
I simple explain that it is NOT illegal to stamp the notes, as we do NOT defeat any of the security measures built into the note. (nor is the serial # or denomination changed). I also explained that once the BOC gets the "mutilated" notes, they simply reissue them unless they have been taped or badly worn. 99% of the time, the bank collectors (LOOMIS, GP2, ETC), rarely even look at the notes. They collect, run through their machines to make bundles, and redistribute.
I explain about the website and our tracking, and how long its been in active service. Sometimes I'll even show them one of my "hits" so they can see what I've been telling them about. I end the conversation by saying, "Check out the website and you'll get all the info". Even show them the OUTDATED letter by the BOC concerning marked notes. They are usually very accepting.
Only once, at a certain bank branch, was I refused accepting my money (even after I stated that this is legal currency). I simply just stopped using that one branch of that bank.