We need semantic markup for sarcasm for the best of both worlds! Style sarcasm with CSS and have your client/browser indicate it to you however you prefer.
The WAI-Adapt task force at the W3C is working on the Help and Support Module to, among many other things, annotate in markup the literal interpretation of metaphorical statements, jokes, and sarcasm so you can style and switch between them. Lots of planning, vocabulary, and proof-of-concept work is done. It’ll take some years for real implementations to roll out and for it to mature; implementation-wise, they’re focused on really basic stuff like adding an attribute to HTML.
Spending time on an HTML attribute sounds petty but this is the HTML Standard we’re talking about! Every browser, e-reader, screen reader, tutorial, course, Samsung Smart Fridge (ok that last one was a joke), etc. will have to support it forever. It takes time to figure out what to do so it doesn’t have to get re-done.
Once that happens, we’ll need authoring tools to let people annotate sarcasm and such before posting. We’ll need to normalize a “write then edit” workflow, where “edit” includes adding alt-text, semantic tone indicators, content-warnings, etc.