... like arcade Gravitar. Where you can get wiped out on the menu screen.
No, they're not that stupid.
But the standards around this aren't exactly models of clarity.
In general, *hostnames* must be characters. And DNS entries that point to websites should also conform to hostnames. But DNS strings can be *anything*. Yes, they can be arbitrary strings of bytes, as long as the top-level domain is valid. The null is legal. Keep in mind that the CA is signing a DNS entry, which may be used for something different than web security.
The problem, as actually stated in the summary, is in the clients. They think they have a character string - they don't. They have a byte buffer of a certain length, and the clients should not be using null-termination based software to process the buffer.
I think running Win98 has become the equivalent of owning a car so old it's now an antique.
There are certainly some ancient rustbuckets out there, shedding parts and stalling at every opportunity. But there are some that are kept clean and well maintained - which is, at this point, actually *more* work than running a newer system.
These aren't blindingly fast, they don't have modern styling, and certain newer addons will never work with them. But they'll still keep up in day-to-day use, and with a little extra smart maintenance, they're pretty reliable.
And - if well kept up, they will be hard to break into while parked.