I’ve picked up a few bad typographic habits writing in HTML/Markdown. From Robert Bringhurst’s The Elements of Typographic Style:

When boldface is used to emphasize words, it is usually best to leave the punctuation in the background, which is to say, in the basic text font. It is the words, not the punctuation, that merit emphasis in a sequence such as the following:

… on the islands of Lombok, Bali, Flores, Timor and Sulawesi, the same textiles …

But if the same names are emphasized by setting them in the italic rather than bold, there is no advantage in leaving the punctuation in roman. With italic text, italic punctuation normally gives better letterset and thus looks less obtrusive:

… on the islands of Lombok, Bali, Flores, Timor and Sulawesi, the same textiles …

Typically in HTML you just surround an entire phrase in the bold or italic tag. Bringhurst urges one to take the time to wrap each word appropriately.

It’s also why I’ve had less interest in XHTML’s “semantic” tags. The idea was to use <em> for emphasis and <strong> for strong emphasis so thet the underlying tags have semantic meaning. Say why you’re adding italics or bold, don’t just do it. But it was always a clunky, programmer’s brain way to do it. You’re supposed to use the <cite> tag, for example, if you’re italicizing because the word is a literary work, but for short stories we don’t italicize citations, we use quotation marks. And of course Markdown was designed to make writing simpler and to keep all those tags from cluttering up your text, yet it uses <em> and <strong> where I think it should use <i> and <b>.