Syntax for marking incorrect examples of language

I have noticed various marks in example sentences to denote incorrect examples of English:

This is correct.

*This incorrectly.

The former is left alone; the latter has an asterisk marking the sentence as a bad example ‐ something to avoid and not repeat.

Is this notation widely adopted? Are there other marks with similar purposes? I have also seen the following denoting a questionable case:

? This would have been maybe debated.

I am interested in the proper usage and formatting of these marks. How should they be spaced? Should they be placed before or after the sentence? If a particular word is in question, should that word get the mark or the entire sentence?

Solution 1:

These are standard in linguistics works. I don't think they are widely used or understood by general readers.

(There are actually two different uses of '*', one marking utterances which would not occur, and the other marking historical words or forms which are reconstructed, not attested; but it is rare that this double use causes any confusion).

I would put the markers immediately before the sentence without a space:

*They wasn't coming

I would occasionally use them to mark an individual word, but normally only when different possibilities are being compared:

They weren't / *wasn't coming