I have suggested using the tilde ( ~ ) for this punctuation mark. It is used to denote sarcasm. When used in this way, it is called 'The Garrett' or 'Garrett mark'. Why 'Garrett mark'? the answer is simple and obvious: "Big G's Punctuation to fame." is too wordy.
How many time have you gotten angry, or confused by a typed post because it's was being sarcastic? How many flame wars could have been ended sooner?
You would use it like so:
"My, what great weather we are having~"
I selected the tilde as a representative of the 'Garrett Mark" for a few reasons:
- It's not used for much of anything else.
- Won't be used to often, so it's placement on the keyboard is good.
- The back tick is too small.
- Easy to recognize.
- Can't write sarcastic language.
The great thing will be, grammar Nazis will have something else to complain about~
UPDATE:
I think it should be changed to snarky comment, not just sarcasm.