Jack Campin wrote: That statement from somebody at Mozilla is just plain moronic.

No, it's just advice. Eventually browsers - or browser-like programs like the webview modules in apps - will reduce their bloat by dropping strict html 4 compliance and sticking to elements included in html 5.

Mozilla are just warning you what's likely to go. You're free to ignore the advice, and my guess it that the old teletype tag will work for some years yet (I'd forgotten it existed) but it seems to me to be sensible to maximise the chances of your code being readable in the future.