Everyone is an expert in their own activity. If they have something insightful to say (or to ask) one trick is to write the comment in their native language and use autotranslation (double check technical words, because sometimes autotranslation picks the wrong synonym) (also check the output, because if the original has a one letter typo, sometimes it's translated to a very different word).

Another possibility is to write the comment in English inside gmail, and let suggestion gmail fix all the errors.