[mwcampbell]

With NVDA on Windows, when I read the comment normally, it's spelled out. When I read it character by character, I get "symbol FFF8" for each of the hidden Unicode characters. And when I move line by line through NVDA's linear representation of the web page, the hidden characters count against the length of the line for the purpose of word wrapping.

Narrator's behavior is weirder. If I turn on scan mode and move onto the line with the up or down arrow key, Narrator says nothing. If I read the current line with Insert+Up Arrow, Narrator spells it out like NVDA does. When moving character by character, Narrator says nothing for the hidden Unicode characters. And because Narrator doesn't do its own line wrapping but defers to the application to determine what counts as a line, the text only counts as one line.

Disclosure: I used to work on the Windows accessibility team at Microsoft, on Narrator among other things.