I think my definition of an alt is pretty broad. If someone is trolling around here under a different name than they used to go by, then, regardless of that previous accounts posting patterns, if he is now just trying to elicit hyped up responses through performative language that is richly informed by our message board’s habits and personalities, I call that an alt.
It’s a troll with too much insider information. To be a troll, you don’t need insider info. To be an alt, you do.
I’m happy to use a different term than alt. But “troll” won’t do.