Excerpt from this article:
The tilde, though, seems to have bypassed that problem. “If I say that your question is wonderful, you’re going to interpret it as the most common meaning,” explained linguist Michelle McSweeney, a researcher at Columbia University. “But if I say that it’s ~wonderful~, you understand that I don’t mean the boring, old meaning of wonderful.”
If there were such a thing as “visual onomatopoeia,” the tilde would definitely be it. The tilde looks like what it means — like it’s shrugging, or swaying in the breeze, like it sorta knows, ish.