The reason for differences in opinion is because many Touch Hole Liners are not removeable. That is, the screw slot has been filed away in fitting the liner to the barrel. To remove them, you have to damage the vent hole with an " easy out " screw, which means you have to replace it with a new liner. Unless you can find one that uses an allen head wrench to put it in, or another brand that allows a slot to remain after fitting, you are looking at a lot of cost just to clean those threads.
I do agree with Roundball on cleaning those that are removeable. Either bore butter, or anti-seize compounds, or even plumber's tape, if it will fit, can keep the threads from being worn from removing the vent liner for cleaning each time you shoot.
I use a pipe cleaner to clean grit and residue out of the threads. If I even feel one bit of grinding when I replace a nipple, or liner, the item comes back out and I reclean the threads. :shocked2:
I use a toothbrush to clean the threads on nipples, and I have used a small brush with soap and water to clean the inside threads in the barrel or bolster. A drop of oil on both before they are screwed back together is all that is needed to protect the threads from wearing out.
I have a vent liner on my rifle that is not designed to be removed. I have not done so. But, I spend extra time with that flintlock pumping soap and water out that vent hole to make sure that any residue in the threads that are exposed are removed. :hmm:
If I find residue on my drying patches that suggest the threads of either the breechplug, or the liner are still Leeching " BP residue, I go back with soap and boiling water to get that remaining residue out. Then I cool the barrel using cold water to flush it of soap, before drying the barrel with patches. :grin:
On the occasional firearm I use that has a removeable vent liner, I use witness marks to tell me where to return the liner to position in the barrel, and I get the "gorilla" out of my shop when turning in those liners. That way, I don't bung up the screw slots, or crush the threads. :thumbsup: