Have any of you encountered this sort of behavior in the past?
Yep.
I have also observed the opposite situation on the Summit, where established characters will only engage other established characters and completely ignore new pilots to the channel. Even established players with alternate characters (who are new) will be engaged much more quickly than the unknowns. Some people do make the effort to engage everyone, but I watch the channel often and I find it rather disappointing when fresh faces make the effort and don't even get hello.
Mind you, I'm not trying to guilt anyone into interacting with people, but perhaps being mindful of this behavior will encourage some not to be so cliquish.
This is mostly why I don't really like alts in Eve when it is about alts of established players - and said players do not want to reveal who they are. Nothing particularily wrong with that of course since it is often a way for a lot of people apparently to take a breath and try something new, but it tends to be annoying since most of these alts are 90% of the time disposable alts. I personnally find disposable alts often uninteresting for the very reason that the player is not really planning to play them seriously or long enough. And even if the character is interesting, it does not last long enough to actually become interesting with depth of personnality.
So, yes, it is not always very compelling to engage in discussions with alts, ESPECIALLY when it looks like the new whimsical alt of an established player that is unlikely to last very long. Which is twice more frustrating is that you can't sometimes tell them apart to real, actual and genuine new players.
Not that I have really avoided very hard to engage in discussions with new players. When my character is on a channel, she speaks and reacts to anybody as the logic dictates it.