An identifier is an arbitrarily long sequence of digits, underscores, lowercase and uppercase Latin letters, and Unicode characters specified using \u and \U escape notation(since C99), of class XID_Continue(since C23). A valid identifier must begin with a non-digit character (Latin letter, underscore, or Unicode non-digit character(since C99)(until C23), or Unicode character of class XID_Start)(since C23)). Identifiers are case-sensitive (lowercase and uppercase letters are distinct). Every identifier must conform to Normalization Form C.(since C23)

In practice depends on the compiler.

The answer to your question seems to (still) be "no".

https://godbolt.org/z/qKejzc1Kb

Whereas clang loudly complains,

https://godbolt.org/z/qWrccWzYW

This seems to have been fixed now.

Or better yet, don't let 'social pressure' influence your choice of programming language ;)

If your workplace has a clear rule to not use memory-unsafe languages for production code that's a different matter of course. But nothing can stop you from writing C code as a hobby - C99 and later is a very enjoyable and fun language.

Of course it's still really nice to just have C itself being updated into something that's nicer to work with and easier to write safely, but Zig seems to be a decent other option.