Last modified: 2013-04-16 08:53:06 UTC
When the right hand margin is shorter than the first text box (for example, when the section or category list is disabled) the first text box expands to the entire width of the page and the right margin floats above it.
According to one of its developer (Mark), Uniwiki extensions for MediaWiki are not under active development anymore "and it is safe to declare them obsolete/wontfix."
It is unlikely that there will be any further active development.
Closing this report as WONTFIX as part of Bugzilla Housekeeping and adding the whitespace entry "extension[unmaintained]". Please feel free to reopen this bug report in the future if anyone takes the responsibility for active development again.