Good find by BirdOfPrey, I wouldn't have thought to do that but it works because an assignment has a value and can be put in a conditional, so you can create an array like Danny mentioned without needing a plugin.
Modifying the mod that BirdOfPrey found, I think something like this should work:
Code:
<if condition="!$vboptions['shownlinks'][$post[userid]] AND $vboptions['shownlinks'][$post[userid]] = true">
// Show user's links
</if>