Not everyone is good in English language (including myself), but at least the text should be readable irrespective of some minor mistakes and usage of tenses. If the text is not comprehensive at all, it should be called a spam.
I don't think it counts as spam if the post is not easily readable due to bad grammar. Not everyone has a local language or local board here to communicate in their native language and attempting to write in English language shows they are making an effort and should improve if they keep at it and take corrections from other users or grammar correcting apps.
Rather than tag such as spam, I think we should have community focused programs to help those willing to improve their use of the English language.