I meant exactly what the parent-comment pointed out - that C can't be parsed without a symbol table. Like the example on wikipedia:

A * B;

Which either represents a multiplication or a pointer of type A* to B, depending what the symbol table looks like. That means parsing C is impossible without these hacks, and you need to basically parse the whole file to build up this information.

A lot text editors which only support grammars can't parse this properly, there are a ton of buggy C parsers in the wild.

The issues that led to this were completely avoidable, and many languages like Pascal (which was more or less its contemporary), Go or Rust did avoid them. They don't lead to the language being more powerful or expressive.

Calling it the 'worst' might be hyperbole, but given how influential C-style syntax has become, and how much C code is out there, these issue have affected a ton of other languages downstream.