I imagine most of these "stylised" effects are generated by services like https://yaytext.com https://yaytext.com Getting those services to include such markup

I imagine most of these "stylised" effects are generated by services like https://yaytext.com https://yaytext.com Getting those services to include such markup in the copy/paste version would probably solve this problem for most occurences. Note that (a) the original text is known to the service and (b) copy/paste content doesn't have to match what is displayed (e.g. "pastejacking")