I can't tell where it's coming from. That does seem to be a bogus reference, as the warning has not been attributed to node.js again since. Annoyingly, the problem does not happen consistently when the developer tools / firebug is open, which makes it more difficult to track down. When it does happen, I see an unstyled page briefly.admin wrote: ↑6 Apr 2021, 2:33pm I have Firefox 87.0 on Linux (Fedora 33) here, and it's snappy as anything else.
There is no use of node.js on this Forum, so I'm not sure where that message is coming from? It's a server-side thing, so are you using a proxy server, or Tapatalk, or a whacky Firefox plugin, or something like that?
My current suspicion is that font-awesome.min.css keeps getting redownloaded (and that delays the following cached stylesheets taking effect) but I cannot yet explain why because the headers look OK to me.