There was a long tradition in English and maybe also in other European languages of choosing punctuation depending on how long a pause a speaker would take at the point, with a comma denoting a shorter pause than a semicolon, which in turn denoted a shorter pause than a colon, which in turn denoted a shorter pause than a period -- instead of using punctuation to convey some semantic distinction as most writers do today. The comma splice might be a vestige of that tradition.

You have to put a semicolon in place of the comma or it is just plain wrong.