You are not damaging any thing after 15 days fasting. You are certainly healing.

I do not know the explanation for that particular experience. But I respectfully suggest you make this very same question in the Iodide forum. I am sure you may get a very interesting explanation there about your throat.

Of course, more experienced fasters will give you soon their feedback here.

I'm gonna take a shot in the dark here: is there any chance that you're experiencing post-nasal drip and that is irritating your throat and prompting a lot of extra swallowing? I had a strange experience in my last fast where I'd think I'd finally hit the "rock bottom" of clear sinuses and then a few days later there'd by another slo-mo, day-long mucus avalanche.

Another possibility involves changes in the production and quality of saliva. These can be pretty dramatic, but if you're not "tuned in" to them, it takes a while for them to register on your radar. Sometimes saliva can get watery or thick & sticky or stinky. Things like this could stimulate your swallowing reflex.

Other than those two ideas, I've got nothin'.