Magento buttons have a button/span/span structure, which I thought was silly at first. But it's really helpful for styling them, because those two elements give a designer an awful lot of flexibility without having to change the templates.
This got me to thinking that writing the templates for modules is more of a technical task than a design one. It's about writing HTML that can be everything to anyone, without any specific layout in mind.
So I have two questions: is the above thought correct, and are there any other similar conventions in Magento that I should bear in mind when writing templates? Things that aren't common sense, but obvious to the experienced developer?