we don't like this kind of feedback in a workshop

[milo]

Oh for writing I think technical skills are very important. I just don't think they produce the most useful comments.

So I could say,

Milo, there should be a semicolon after important instead of a period!

or I could say,

Milo, I think you could have phrased the last sentence in a more interesting way, perhaps: "I think they are monopolizing space in which more valuable comments could reside." Or something to that tune.

exactly.  The first is just an editing suggestion and will in no way make the poem better or even help me to make the poem better, just more technically correct.  The second lets me know there is a fundamental flaw in the writing that needs to be fixed so I know where to focus and why.

I think it is good courtesy to point out editing suggestions but I wouldn't consider a post with only editing suggestions to be acceptable commentary for a workshop.