So we make a new rule that prohibits it. That's what this whole argument's about, ma dood. The legality of aliases
It seems to me that there are two distinct issues: the morality of aliases and the legality of aliases.
Morality of aliases: Assuming there isn't a rule, would it be morally right to use an alternate alias?
My position: It would be morally permissible assuming he's seeded properly. If he wasn't seeded properly it would either make things worse for sheer, or worse for others, depending on the randomness of his seeding. Thus, it would be morally right or wrong depending on the randomness of the seeding.
Legality of aliases: Should there be a rule to stop sheer from using an alternate alias? If so, why? If not, why not?
My position: The first problem with sheer being allowed to use an alternate alias, I think, is the following: if everyone followed suit and used an alternate alias. If everyone did this, it would result in random seeding. But I doubt anyone would agree to random seeding. This is because the tourney wouldn't really have accurate results in regard to who's better than who. Thus, it's likely that even if sheer uses an alternate name, and is seeded randomly, others would not follow suit. Again, this is because the tourney would not have accurate results. Also, they could get eliminated unusually early or late depending on luck.
Second problem: If he's not seeded correctly, there is a problem of unfairness. But this would depend on the randomness of the seeding. Note that this could work against sheer's favor: e.g. If sheer plays Isai in the first round.
TL;DR: A rule banning aliases should be implemented if he is seeded randomly and tourney hosts want accurate results. If he's seeded properly there are no problems.
Extra: Would it be more fun for sheer to use an alternate alias?
My position: Apparently he thinks it would be more exciting and tougher, assuming he's not seeded correctly . If he is seeded correctly, I don't see how that's any more fun for him.
Is it fun for others? If people don't figure out who he is, get ready for a pleasant/unpleasant surprise depending on how good you are.