I wouldn't say "Reddit reads Sam" is semantically meaningless. It can mean the Reddit community forms an understanding of who Sam is, or just that they read words Sam wrote, depending on context.

I would say the rule has been broken if the speaker intended to communicate that Sam was the one reading but they said the words in the wrong order, perhaps because they didn't know English grammar well. It's a particularly bad mistake because it may lead to a misunderstanding.