Ok, I analysed it further. The 'suo' snippet is working properly, it generates a [[div class="suo-specific-class …"]], so that the wiki interpreter closes the previous <ul>, and a new <ul> is opened (in the menu example).
So it seems not possible to keep on the same <li> chain with a 'suo' snippet inside :-( (the Community site works fine because of CSS, but the submenu "Internals" is on another <ul>, not in the same as the rest of submenus).
Anyway, the 'alt-suo' snippet adds the following extra output before the main 'alt-suo' div, in fact there are two "suo-specific-class" divs for each snippet in the source:
<div class="list-pages-box">
</div>
<div class="suo-specific-class suo-enrique-santos suo-normaluser">
<p>.</p>
</div>
(sometimes a different output, probably Timothy is working on it, thumbs up!).
I'm using the solution proposed by Timothy with 'alt-suo' snippet, it works fine ('suo' doesn't show anything to anonymous users).