If you're going to do that then only do it for email addresses where you understand the local MTA conventions (like gmail). Do not do it for domains you don't know (because you cannot predict how they work).

For instance, on my email domain, [email protected], [email protected], and [email protected] are all the same ('+', '.' and '_' all act like you'd expect '+' to), but [email protected] is not (it get's picked off and aliased somewhere else). Applying gmail conventions to other domains is silly and wrong.