<noscript> works just fine in pre-JS browsers, at least all of the ones I've tried.
It works exactly as designed: Text between <noscript> and </noscript> is displayed in browsers without JS enabled (or supported).
I am not aware of any browsers where this is not the case, and I've tested in many, including Mosaic 1.x-3.x, NN 1.x-4.x, Opera up to 3.62, and others.
(You probably happened to visit my site during an upgrade. Sorry about that.)
Strict validation of HTML came later with XHTML, but AFAIK all browsers which understand XHTML also understand JavaScript.
However, HTML 2.0, which you can find specified here [0], and it specifies the "ignore" behaviour. Short of spinning up an old VM, I think I'll trust that my memory hasn't failed me.
From RFC 1866:
> markup in the form of a start-tag or end-tag, whose generic identifier is not declared is mapped to nothing during tokenization. Undeclared attributes are treated similarly...
> For example: > <div class=chapter><h1>foo</h1><p>...</div> > => <H1>,"foo",</H1>,<P>,"..."
Many of the 3.1-era browsers didn't have a concept of JS yet. If you're relying on noscript at all it won't work.
I did try and check if this was the case, but both links in your profile that it could have been lead to "not found" dreamhost sites.