Tone can be expressed over text on the internet, details inside.

[a completely inoffensive name]

Perhaps typing "[/SARCASM]" or something similar can do the same and be a lot clearer than a symbol that few people know about.

But that strips the sarcasm of any elegance it might have. It's very blunt and takes away the ability to enjoy it because your eye spots it immediately and prepares you for it, which ruins the effect of it. A different punctuation mark allows for the reader to go about and take in the sentence without any presupposition of its contents and then receive the context at the end.

[Tellos Athenaios]

I'd rather have support for markdown or restructured text than something obscure which few people will understand. Especially if the aim is to improve on semantics which are in any case supported well enough through more eloquent use of English, implicitly understood, or easily made hinted at in other ways. The ORG has a particularly fine collection of smilies, for instance.

[TinCow]

Tellos' concerns are mine as well. The proposed punctuation would work well... if it was commonly understood. I doubt most people would know what they meant if they showed up in threads, which would defeat the purpose of using them. I'm a pretty well-read guy, and even I wouldn't have known what they meant if someone had posted them in a sentence prior to the creation of this thread.

Interrobang I think is commonly understood, but no matter what we did it would be far more work to type the code for that icon than to simple type ?!. Where's the time-saver there?

[Beskar]

You could make the icon be ?! so it automatically changes ?! to ‽

[TinCow]

You could make the icon be ?! so it automatically changes ?! to ‽

I don't know about anyone else, but that symbol looks horrible on my screen. It's so tiny and blurry it's hard to tell what it is. The ?! itself is far easier to read.

Test:
what‽
what‽
what‽
what‽
what‽
what‽
what‽
what‽

Hmm... this one (‽) might look ok. Thoughts?

Actually, it would be a bad idea to substitute a specific font size and type, as it would then display improperly if the interrobang were used in a non-standard font size. So, it would have to be the same size as the text.

what‽
what‽
what‽
what‽

It looks fine at larger text sizes, but the top one above is default and it looks horrible there.

[A Nerd]

I think the sentiment will be lost and therefore unappreciated for anyone doesn't understand the system and cares not enough about the new system to research it in order to use a symbol that can they can already express with seemingly less effort. I guess this new fangled interwebz lingo mumbo jumbo is just too cutting edge for me.