It happens the same to me. I think it shows the gravatar that corresponds with the user's email, and if not the default avatar image. I would prefer if it was the forum avatar thumbnail instead of the gravatar.
I have another question, is there a way of changing the order of the blocks in the portal page? For example, I want to have the most recent links at the top and the links with most hits at the buttom. I searched in the settings but I couldn't find the option.
I have an error with the search in the links section since I updated to the last version (a week ago more or less) and another small error with the secondary navigation. I explain more details below:
The search of the word, for example "discoteca", gives 3 results which are ok. The problem is with the link. When I click on any result it takes me to the home page instead of taking me to the link page.
Another problem occurs when the keyword is in the title of the link, it shows a strange code:
Finally there is another minor problem related to the words at the top of the category pages. Instead of ending in the name of the category, it ends on the name of a random link: