According to the Answer here, Sublingual tablets do not need to be kosher. What about chewing gum, does it need to be from kosher ingredients? It’s also not swallowed. Also usually the non-kosher ingredient is the gelatin as opposed to the flavoring.
Gum must be made of kosher ingredients. Does not make a difference if you swallow the gum or not.
Everything you put in your mouth must be kosher. Not swallowing is not a valid argument. In the post you quoted they were discussing medication. Medication has it’s own set of rules.
Gelatin is kosher because although it may be coming from a non kosher animal, gelatin is made through a process that makes it inedible. As an inedible ingredient, it is kosher.