I also wanted to add:
If
@a, b, c
def func(): ...
was prohibited (i.e. you must use parentheses) because [it looks like] it doesn't make any sense,
No, It is because tulles aren’t callable. So it CANNOT have a meaning.
shouldn't be also the case that any expression with spaces should be parenthesized? Because this looks equally "wrong":
@a + b * c**d % e
def func(): pass
A set of overloads could be devised to make this do something useful.
Granted, there is no rule resembling this anywhere else in Python, but maybe an exception can be made here, to keep it consistent with the above?
What consistency? The consistent rule is that the grammar doesn’t judge what users want to do with the language.