Usually the majority gets it. And the worst that can happen is that some people will downvote you, or call you an idiot. I'm not especially concerned about this.
I don't see how it's an accessibility issue, except to help out those with a deficient sense of humour.
regarding accessibility..from what I have heard, other cultures have much different styles of sarcasm which might impede their ability to understand that something you have said is sarcastic. e.g. Japan is known to have a reputation of not understanding American sarcasm, but has it's own style of sarcasm. (see https://linguaholic.com/linguablog/sarcasm-in-japanese/)
so, I guess announcing your sarcasm makes sense in an international accessibility sense, particularly when some of the normal cues are not present (tone of voice, facial expression, eyes rolling)
Communicating across cultures is always bound to lead to the occasional misunderstanding, even more so over text. When writing something "dry" such as documentation it's probably a good idea to keep that in mind, but making jokes worse just so that a few more people can perhaps maybe possibly understand it is where I draw the line.