When to harvest calabrese?

[Snoop Puss]

Depends which plants are more important to you. If you remove the leaves, you're removing the plants' source of nourishment through photosynthesis.

What are the other plants and what kind of spacings are you using?

[Penellype]

Stupid question, but is it worth trimming the leaves to allow more sunlight to other nearby plants?

I wouldn't trim the leaves (although I remove any old ones that are going yellow).