You're right to be sceptical about TA. A lot of major firms with a lot of money and a lot of very smart people have tried, and failed, to develop and implement TA in a variety of different markets.
The underlying premise, that there are repeated patterns, seem to be flawed
That was my impression too.
Plus, the logic underlying TA -- that all causative factors repeat over time, so extrapolating patterns over time automatically factors in those factors without explicitly identifying them -- seems, like you say, not quite impossible, but iffy.
That said:
and in any case, the first functioning TA process would in any case "break" the pattern by seeking to take advantage of it.
This will apply for any opportunity, arising out of any kind of price discovery mechanism, not just TA. Besides, market efficiency is always somewhat wanting, leaving open one those window of opportunity things for limited time periods.
The idea that a single individual with a spreadsheet has succeeded where financial institutions have failed is remarkable, but not impossible.
As you say, remarkable, but not impossible. That kind of thing does apply to identifying pricing inefficiency via fundamental analysis as well, throwing out a very few truly exceptional fund managers. (Although even the Warren Buffets occasionally trip up, or put in very pedestrian performances.)
I was commenting only generally, not speaking of Samson's claims. That I suppose can be directly evaluated, by him, or anyone else who's interested in his specific claims, by charting actual performance against claims? Should be fairly straightforward, I should think, should someone want to take the effort to do that charting.
If I were that person I would either keep quiet and go on to amass a huge fortune using my TA directly and/or by selling it to a major financial institution. I know it's an argument from incredulity (and hence a logical fallacy) but the idea that someone with a working TA algorithm wouldn't use it to make themselves rich and would instead boast about it on a minor forum in the backwoods of the internet beggars belief.
It reminds me of the psychics, who claim not to be able to use their "gift" to make money
I take your point, this makes sense generally speaking; but I'm not sure I agree, as far as this individual poster. I mean, sure, your POV is logical; but then what you say might apply to everyone who holds forth in these forums. We may argue, then, that the physicist -- and biochemist, and mathematician, and philosopher -- would better probably employ their time in actual research or study or discussion with equally knowledgeable peers or something, rather than pontificating on here, so that the one who does post here is probably some kind of poseur. While sometimes/often true, clearly that's not always the case (or at least, I think not, and hope not!

). Different people may have different reasons for posting here as opposed to spreading the light of their knowledge in the world at large, and benefiting personally from it.
I'd rather not comment specifically on Samson's claims. (That, after all, can, like I said, be evaluated directly by graphing out the data points vis-a-vis his claims, should anyone want to do that.)
But absolutely, I share your general skepticism as far as TA itself. The thing sounds very much like, as you say, psychic reading or astrology or reading tea leaves (or skirt lengths!). And yes, to my (limited) knowledge, no one has, as you say, actually shown TA to work consistently. (I guess if it did ever work -- if if IF -- then it'd had to be run by, like you suggest, a relatively small operator working quietly, so as not to trip up the market and upset the magical patterns.)