In this video Flieger makes some good observations. Nothing here to change my opinion about the pipe filter's PITA factor; but none-the-less useful to know. Thanks for the post.
As to a wet smoke being related to salivation, I have a hard time accepting that. I imagine it would be difficult to accumulate a significant amount of moisture even by forcing the saliva in, let alone doing it unintentionally. That's why I suggested, IMHO, more likely causes: room RH, tobacco moisture, and smoking cadence. Warm air holds more moisture than does cold, and condensation results from a cooling smoke stream. (I think this is, in part, the rationale behind the Savinelli system.)
Well, the only way to verify any of this is by empirical observation. Since you've presumably smoked unfiltered pipes and found them wanting, I don't exactly know what to do with your opinion now that I have it! LOL