The question has been asked several times on this site:
Can we provide follow-up to our questions? Yes, we can is the unanimous answer but what does not seem unanimous is the method of the update.
It is split between two methods: answering your question or editing your question.
Can we have some final consensus over this? I would very much like to provide updates to some of the questions I've asked and received help for but would like to do it in the appropriate way.
Should we edit the question or should we answer the question?