Actually, @bretfausett there is a class of people who are banned from using HTML... https://twitter.com/bretfausett/status/1350543259634855937

Under 37 CFR 57(e), patent agents and attorneys are prohibited from using HTML in patent specifications. This is the one federal regulation for which I am accidentally responsible....

After @carlmalamud was successful for dragging the USPTO kicking and screaming online, the USPTO's browser-based search system had a "full text" option for retrieving patents. It would simply feed the raw patent text to the browser, but...

Some patents had HTML code examples, which caused amusing unintentional results when the patents were retrieved - remote images, external links, buttons, forms and other webpage regalia. It was pretty funny, but on Usenet I suggested, as a joke...

...that you could intentionally incorporate HTML that would draw in remote text, so you could change the text or claims of your patent at any time! Well, someone in the USPTO didn't think it was funny...

...and the IT folks couldn't explain that it only required a simple fix in the way the USPTO served up text. But an emergency practice memo went around, banning HTML in patents. But then, you could be required to include HTML in patents if the invention involved HTML... so...

It ultimately ended up as a form rejection, but "Examiners should not object to hyperlinks where the hyperlinks and/or browser-executable codes themselves ... are necessary to be included in the patent application..." Doh!

Eventually, though, they fixed the issue with serving up raw ASCII text streams to a browser. But I am the proud owner of a US federal regulation banning one of my ideas!