Useful if 1) your text processing system can embed SVG, and 2) you have the desired font available for SVG to use. I don't know how serious these constraints are (particularly number 2) in practice. And of course, the source I give is oriented towards HTML/CSS (browsers and their converters to other formats), and not something like LaTeX.
Certainly, I welcome someone re-doing the examples I gave using SVG. Even on-the-fly creation of embeddable pixel graphics (.png, etc., created at the proper scale) are welcome. The whole point of this exercise is to come up with ways other than embedding pixel graphics created at a fixed size into text. They should be seamless (i.e., the viewer can't tell that they're not normal text, even under magnification).
Also, don't forget that not all special punctuation is available under all fonts. For example, while ©, ®, and ™ are widely available, symbols such as ℠ and ℗ may not be.