It's true that when I am reading fiction and I see something that is important to me done badly, I really notice it, out of all proportion I suppose.
I noticed in in HP fanfic, all those Americans writing about Graduation and Proms annoyed me (not that such things are important to me, but it was suprisingly annoying), it ruined a perfectly good Dr Who fic for me when the writer had the 8thDoc riding a motorcycle with a foot accelerator.
I see musesfool
feels the same way about sports.
I haven't read much commercial or fanfic lately that does much swordfighting. I have come across ones where the hero has a crowbar weight sword either because that means he's so manly  or because the writer has some idea that all swords are like that.
I swallowed The Incompleat Enchanter's idea that an epee fencer might outdo a Viking swordsman because a) the Norseman's sword would be really heavy and slow, and b) the big muscly guy had no idea, but that was a long time ago, and I don't think it washes now. I still see the meme in fantasy books though (not to mention a certain iconic movie) that some untrained but Pure peasant can get a little training and in his first fight completely outfight people who have been killing other people with swords for years.
Doesn't mean novice can't beat experienced, I've been taken out by new fighters often enough to know that even Homer nods. Still, that's in play and I feel uncomfortable monstering new fighters so I don't tend to unleash on them. If it was lethal fight then experience in "real" can trump a lot of skill - ask Aldo Nadi who at the time he fought his one and only duel in 1922 was generally considered one of the best if not the best sport fencers in the world. He was terrified when that sharp sword was heading in his general direction, and was touched by it several times. joyful_molly
has a list of resources for age_of_sail
that includes a link to The Association for Historical Fencing, but I suspect that they'd get something more useful from fight directors who could help with having a reasonably realistic fight which also advances the plot. (artpfcombat.org seems to be down at the moment...)
I learned a lot about theatrical fencing from my fencing master who has directed plays and even commercials. How to use technique to advance the plot. The obvious movie example is The Court Jester, Dave Luckett did a reasonable job in his Tenebrae trilogy, anyone got any examples where the swordfight was clearly a useful part of the book rather than "swordfight cliches #2 and #6, check"?
Any that really struck you as "you are *joking*"?
Cornwall's Sharpe has sort of an excuse as the heavy cavalry sabre is at least only marginally bigger than an infantry one but the Sharp's Sword movie made me throw things at the screen.)
 for one thing, your average modern epee fencer doesn't get off line by more than a few inches due to spending all their time on a piste, so they are really relying on a stop-thrust stopping that broadsword from blowing right through their 500gm needle on its way to slicing them up. And they had better get that needle into a bone or an artery or some very vital organ because that sword is still coming even if the bod is dying next day from a puncture wound gone septic. See Frank Lurz's "Dubious Quick Kill essays on http://www.classicalfencing.com/articles.php