Not everyone on the Internet is an Anglophone, nor does every piece of software store and render Unicode correctly.

Many languages use different delimiters, and their keyboards might be set up accordingly.

Eg, in French one uses ‹single› or «double guillemets», and CJK languages use 《more angle brackets》 or 「corner brackets」.

I'm not familiar with question marks being used that way, but let's give people the benefit of the doubt. ;-)

https://en.wikipedia.org/wiki/Quotation_mark#Specific_langua...

What's wrong with doing that"

I've never seen it before.

Seems a reasonable text symbol for sarcastic air quotes.