The article name uses a level one heading. From a code semantics perspective, additional level one headings indicate additional articles, rather than additional sections in the same article.
Of course, code semantics don't always translate into human semantics. For instance, a lot of things are semantically lists (such as the toolbars) even though they aren't rendered as such.
Personally, I think the level one headings look bad--they seem too big. If a page has only a few sections, there's really no reason to use it; in fact, if it starts getting used routinely, it'd be breaking convention from most other mediawiki-based wikis which isn't good usability (consistency generally makes for a better end-user experience unless a specific situation warrants otherwise). But if the page has so many sections that it starts needing more than three or so levels of organization, it can make sense to use.
Alternately, if an article starts needing that many section headings, it might also benefit from being divided up into separate articles. (Easier said than done, of course.)