(1) Professional writing style.
Just because someone knows how to write and has a knowledge of forum posting etiquette doesn't necessarily mean that is an alt account. Forums have been around for many years before bitcointalk so for some this is not the first forum.
(2) Offering unsolicited sort of professional advice and help to others on the forum about forum activities instead of being a newbie who is supposed to learn to walk before running.
That is a classic sign that it may be the case of alt account, newbie that immediately starts creating topics telling others what they should do on forum hoping that they will scoop some easy merit. Luckily, other members became quite good at seeing through those attempts.
What is the likely origin of professional newbies here in forum;
Is it Origin 2? (Probability of being an account owned by a user who is already a member here)
Every once in a while a legit newbie shows up but more often than not its just the alt account.