Alters and schticks can -- and have been -- done well. I think the best example would be Victorian Guy, Satanic Goatslayer and Muscular Gunz.
I think the real problem with alters and similarsuch on EF is that they are done too often and for the wrong reason(s). A mandatory ingredient is humor that can be appreciated to a generalized extent... and not denigration towards a certain member or members (or moderators, administration, etc.).
On EF, the word 'alter' seems often synonymous with 'new username of a previously bannd member'. I don't really think of that as an alter, viz. alter ego, as much as an ex-employee trying to spite the company he or she once belonged to.
I can attest to alter-egos being around for quite some time. They were originally called sock-puppets on FIDO and other older messaging systems. Usenet is full of them.