I would advise to split this patch into adding bold and italic feature and adjusting defaults.

Don't see any problem with bold/italic implementation, but with de faults I would like another opinion, I don't feel confident evaluating aesthetic stuff. Overall it seems better, but these changes are quite arbitrary to me.
Box margin works exactly same though, you have just changed range from 0-1 to 0-100 with different effective step size.

Ok. Here is the Bold & Italic patch alone: P2002, but let me remind you that I presented new text presets almost a year ago. First as subtitles according to BBC standards D7714 and then as centered D7768 and now incorporated in this patch. And during all of this time no one else than you and I have been engaged in the discussion of the default settings of text strips, so I think it is a bit optimistic that yet another patch, will make people want to discuss these things.

The trouble with the current defaults are ex. that the text size is that small it'll only fit for SD resolution(which is not the current default resolution), it is placed at the very bottom, where no one will need it(not as subtitles nor title), and you'll miss it if you have the preview zoomed just a bit in, there is no text wrapping, who would need adding text outside of the screen as a default? The margin is moving in odd increments, and why should it be in fractions, it's a magic number no matter what. Also the position ranges are currently way too limited(0->1) to do rolling credits, or have large text animated in or out of the screen.

With a position range of -10 -> +10(not added in this patch) something like this can be done: