For years, Kaufmann and Moore have had regular chats during which they collaborate on development issues. Use the acl2-devel mailing list to continue that tradition. For example, if you are trying to get oriented about the waterfall and how hints interact with it, you could query the acl2-devel list and maybe someone will point you to the documentation topic, hints-and-the-waterfall.
But please don't use the acl2-help or acl2 mailing lists for developer-level discussions, as that can spook users. The acl2-books list also is not the right place; note that it is missing at least one important member of acl2-devel.
This is the final topic under developers-guide.