I seems to me that Ray Walton's ongoing use of braid as a mainline never fazes the barbel he catches...which often runs into several hundred fish per season. Nor those of the thousands of other anglers that took his advice and use it still. I also find it hard to believe that if it became obvious to him, or any angler, that such line was damaging fish...that it would still be in use. Can you imagine the furore that would ensue if fish were turning up in the H.Avon with the sort of damage that some attribute to the use of braid?
Come to that, it didn't put any of the carp off that I and many, many others caught over the years either....nor to my certain knowledge did it ever damage any of those carp. Repeat captures by those fishing carp fisheries, and the lack of bodies showing signs of such damage pretty well guarantees that.
I rather think that not even Paul Daniels could come up with a fishing line that fish cannot see...if it's in their environment, they see it, in my opinion. My guess is that it's not what they see, but whether it moves/acts suspiciously that spooks them. And they
definitely don't like coming into contact with a tight line of any sort. Damage to fish by the use of braid? Possibly mouth damage, in my opinion...if we are talking ULTRA thin braid as a hook link....but the same damage could result from any ultra thin material...and does....I have seen it done by nylon mono many times. Same goes for body damage and scale lifting. I HAVE seen that occur when anglers were using mono, but not by anglers using braid. That is not to say that braid won't do the same...I believe if certainly would if the circumstances were the same....I have just never seen it (Probably due to the fact that the majority of anglers use mono, rather than for any other reason)
I rather think this debate could run for ever, like all hotly disputed issues in angling...they run and run. It's all part of what makes it what it is, I guess
Cheers, Dave.