First you must understand what the default avatar spam agent programer does, first he needs to use a search engine to find your site and in this case every Oxwall site by using a search key word. Then he/she will create a template to automatically register and that will be using the normal default profile questions for Oxwall sites. i know this as I developed software to register users on to search engines. This is all old hat so to speak.
The way to make things awkward is to create 2 or 3 extra questions at least 2 that are required to your profile questions. This means anyone that uses the agents software needs to come back and manual register on your site. Very few will if any.
So you can ensure nobody can publish anything on your site, you could create a green room this means create a new default roll. Say call it newbies or vistors, what ever you wish. But make sure everything is un ticked.
This means you can vet all people that register on your site prior to changing their roll to full member ship. You will find your site spam free.
The main thing however is the profile questions which are normally the complete answer to stop the maximum amount of spam.
But removing the branding tool tip titles will give new Oxwall users total protection to the default avatar spammer and complete privacy from any spammer that uses the same principles.
Mean while I will find the default avatar spam agent and am in the process of detecting the bot by developing software to do so my server.