When I choose a blog theme, there's really one thing that really matters to me: block quotations.
I discovered that the criterion alone can filter out about 95% of the themes offered by a blog service or a theme chooser. Previously I attempted to use criteria such as font family (sans serif typefaces for blogging in English; serif ones for blogging in Traditional Chinese) or overall design (one-column, minimalist, high contrast). But those are vague ones.
How one theme lays out block quotations, on the other hand, is very easy to judge. It either works or doesn't.
I use block quotations a lot. It's a habit I learned at graduate school, where you learn how to appreciate the fact that your idea seldom comes out of nowhere—there are always precursors and you always learn something somewhere that becomes the foundation of your idea. Block quotation is the writing tool that expresses such appreciation.
And in HTML we have the blockquote element. Tumblr happens to make block-quoting freaking easy by choosing Markdown as its default syntax1. So there's no reason not to block-quote people when you should do.
That's where so many blog themes fail. They fail to present a functional block of quotation. Sometimes the indent is not right. Sometimes they just bother to put a big quotation mark, with CSS tricks, beside the block text. Those don't work. Some of them are not even visually acceptable. They hurt my eyes.
So I've got a better filter the next time I want to choose a new theme. Just first test if it handles block quotation well.
Even better, Tumblr extends Markdown a bit so that endnoting is also freaking easy, which is why I think Tumblr is so cool. ↩