The NIN LB one is not that rare tbh (that is covered by a high-vis universal auto LB plugin). It's been easier to spot after I did some research on its behaviour, it's a bit better than "this person's skill use outside of LB is not very consistent" anecdotes now. As I'd covered elsewhere, it's easiest to spot in FL. If a NIN is running Smite (and who wouldn't, I mean really) you will see that plugin will attempt an LB no matter what even if Smite would invariably be the more cost effective move to do. You might never see Smite being used by that player for that reason. Also the plugin is not perfect it does fail. It gets caught up in weaves like any player would and thus acts too slow. If there's a sudden rise in Swift-using NINs now you can blame me. Also tabbing furiously could be a tell if the user is not utilizing the auto-seek feature trying to look more clean.

What I have seen in terms of misunderstanding whether one has spotted it or not? Well, "that player wasn't even targeting me and came out of nowhere!" is a common one, and that's explainable with mouseover macros without the /ta <mo> part added in. A macro I use across multiple skills. However on stuff like SAM LB I've purposefully left it out so apart from the vague direction I'm facing, you won't know who I'm about to strike. Just a bit of casual trickery~

Also Ankhira did imply in a later post they knew Swift's 100% exists, regardless of whether a video exists, perhaps a benefit of the doubt pass could be granted. Not everyone is recording their every move, and a fair enough report would be "I did not notice the Swift buff on the enemy player or anything that could explain this increase in speed, therefore it felt quite suspicious to me" and away you go.