For example, following common formatting I've seen in English style guides:
He went to the shops
Him went to the shops *
Or maybe italicizing bad sentences:
He went the shops
It's common practice in linguistic circles to mark a sentence ungrammatical with an asterisk, and of questionable grammaticality with a question mark.
Anyway, I'm absolutely for this, and it should be part of the faq.
Although it's not very readable, we can strike out the sentence.
Him went to the shops.