I've recovered lots of wads from my paper patched rifles ( well, just the bullets are patched, not the actual rifles

.
The LDPE ones show paper imprints from the patch folds at the base, but no flame damage that I've ever seen, except when using FFFg and getting some gas cutting. In that case you can see the cuts in the wad.
Today I recovered a partially burnt 0.030" wad that was sitting under a lube cookie. That surprised me as I've never seen one with burn marks before.
I've never recovered a felt wad, but have only shot a couple of hundred probably. Most of those were behind breech seated .32-40 bullets.
I was recently given a bag of .45 cal felt wads which I will experiment with soon.
Several years ago Dan Theodore told me of some testing ( bpcr rifles ) with veg, ldpe, and hdpe wads. He was testing to see how wad types affected bullet finning as the lands engraved the base. Veg wads had the largest fins, ldpe were smaller, and hdpe eliminated them. I have recovered patched bullets that were seated under a 0.030" veg and a 0.060" LDPE and found very small fins where each land cut the base.
That's a little ways off of John's original topic, but it is wad related and maybe of interest to someone.
Chris.