Which utility, extension, tool or language is that?

It's from an haproxy configuration file

This unfamiliarity is why I try to use programs that more HN readers are familiar with, like curl or wget, in HN examples. But I find those programs awkward to use. The examples may contain mistakes. I don't use those programs in real life

For making HTTP requests I use own HTTP generators, TCP clients, and local forward proxies

Given the options (a) run a graphical web browser and enable Javascript to solve an archive.today CAPTCHA that contains some fetch() to DDoS a blogger or (b) add a single line to a configuration file and use whatever client I want, no Javascript required, I choose (b)

    :set shortmess+=I

But really, I cannot understand what your problem is with it.

I only use it when a seller doesn't offer any other way to pay, but there are still many, many sites that have it as the only option. A major one is Discogs; also quite a few artists on Bandcamp.

NUL was often sent as padding to slow (printing) terminals. Although that was just before my time.

Maybe 32 was a bit much, but even fitting a useful set of control characters into, say, 16, would be tricky for me. For example, ^S and ^Q are still useful when text is scrolling by too fast.

Back in early times, I used to type ctrl-M in some situations because it could be easier to reach than the return key, depending on what I was typing.

Its inscrutable undo and redo behaviour is probably the main reason why I never really tried to get further into Emacs. And that's when I had just access to original vi, not vim.

My bank's app uses Google Pay to pay at POS terminals, so Google can at least block that.

Very privacy sensitive? In Germany, maybe. Elsewhere in Europe, not so much. See the regular attempts to push through something like chat control.

PTT = push to talk (at least that seems the most probable match on Wikipedia)