@bille Adding resin to your example is what i am describing.
A tshirt saturated with rein won't soak up water after curing, but if you were to sand the edge exposing the fibers, would the fibers be able to soak up water?
My contention is that after carbon or glass is saturated with resin, even if you sand the edge, exposing fibers, that the fibers won't soak up much water. You can dry it off, lightly skuff it and bond to it/paint it etc.
If you try that experiment with kevlar water will soak in and if it's salt water you will never get the salt out.
You will need to glass the salt in and the fuzz down; being careful not to sand back thru.

There is a whole big thread out there in cyberworld about honeycomb & Acats. Some of them use it.
Billl Higgins' Stilletos most definitely were made using aircraft honeycomb and prepreg.
Problems with honeycomb delam seem to be worked out. Once honey comb got to Tornados, they never looked back.
They still have wood rudders and maybe the boards too. I think he does prepreg over the wood.
Also there were honeycomb surf boards in the 60's that are still around today.
So all the cool kids have honeycomb/prepreg these days. i assume: the AC 45's and 72's, some Ccats, those big 60 and 70' tris, but that isn't my field so not 100 percent sure about some of those boats.

As for trailing edge thickness-it's personal taste. You want them as thick as possible without slowing you down too much.. I think if you leave it perfectly squared off. you will get humm. rounded corners-no humm, but is it slower?

for future readers: For this particular repair it sounds like; try a small fill job first, and if it keeps chipping off, make it into a bigger job. one way would be to grind both sides down enough- (roughly the thickness of 3 layers of material), say 2-3" in from the trailing edge, so that after you glass it, the result will fair down nicely. The stronger the materials that you use, the better the repair will last. And off course customize the the trunk so that it isn't as likely to damage your precious foil.