“I think we would all agree that parents should write a nice sincere card to express their appreciation to a shadchan once their child goes out on a couple of dates- wouldn’t you say? Why isn’t that “shmearing”.”
You really have to ask? NO, writing a nice note is NOT shmearing. It is good manners. Shmearing, when it does not apply to bagels (though I guess in this case I suppose it COULD refer to “tuna bagels”) specifically means giving a bisseleh gelt to someone as a bribe. And you know it.