that just means Office 365 has a bug in it, not that using that feature is an "email hack"
the plus syntax is part of the email address specification. any server that doesn't support it is by definition buggy because some mail won't work as expected or designed.
I think you're talking about just allowing the symbol. The plus sign is an allowed character in the local part in the spec. But mailservers are not required to treat it specially and apparently Exchange doesn't. That seems to be the thrust of the comment you answered to.
Tangentially, what's impossible to solve is all the developers out there who build input forms that will not accept an address with a "+" in it and flag it as invalid. They just use a regex that looks for alphabets, numbers, underscores, dots and one @ sign (I've also seen forms that won't accept any TLD other than .com).
the plus syntax is part of the email address specification. any server that doesn't support it is by definition buggy because some mail won't work as expected or designed.