I don't think that a non-native teacher is at a disadvantage in an online arena such as enotes. A couple of things I think would help would be to
1) Look at the age of the student and adjust your explantion accordingly. A high school student is going to have more background knowledge than a middle school (6th-8th grade). The older the student (i.e. senior vs. freshman) will be better prepared for a more complex discussion.
2) Give us much detail as possible when giving answers. I think this is important for all answers on sites such as enotes because the opportunity for follow-up questions is there but likely not to receive an immediate response. If you give too much information, the student will be able to skim through it quickly and get to what they need. The less prepared student will have to read the introductory information more carefully.
3) Since most of the posts are from high school students or first/second year college students, do a search for high school websites in the subject you are answering questions to get a better idea of what is being covered.
4) Look at other questions ro discussion posts being answered in your subject and you'll get a better idea of what other editors are saying and the depth level of their explanations.