Typography matters. Bad typography can be as much of a barrier to the reader as bad writing. Conversely, good typography can simplify the presentation of complex content. This is especially true of mathematical formulae.
Unfortunately, there doesn’t seem to be a standard way to decently render formulae for the web — and basic HTML simply isn’t expressive enough. MathML seems to be a fair attempt at a standard, but like any XML language, it is overly verbose and hard to read. Also — not an entirely fair measure of quality, but nevertheless of practical concern — there doesn’t seem to be MathML support in WordPress, nor any easy way to enable it.
Instead, developers seem to have rallied around the idea of rendering LaTeX to an image that can then be included. This at least allows the formulae to be viewable with practically any device — but if you care even the slightest about typography, you will lie awake at night because of the alignment, spacing, typeface, and scaling issues that come from trying to make an image, not look like an image.
These issues are not inherent to the rendering, but rather a consequence of the way images and text interact in HTML. Indeed, the rendering has its own alignment and spacing issues, that varies between rendering services. To my eye, the best service is the Google Visualization API, which has LaTeX rendering as an undocumented feature. That’s not to say that Google’s rendering is without issues — it has a tendency to place symbols too close together, and has no apparent way to influence even basic formatting.
An alternative to this is MathJax, which uses a combination of HTML, CSS and Web fonts to render formulae as text. In theory, this should alleviate many of the issues from image-based approach. In practice, the typography is horrendous — most notably, nearly every character, number and symbol is italicized. Bad!
As a compromise, I have settled for using basic HTML formatting when possible (e.g. for subscript) — this makes inline formulae appear fairly coherent with their surroundings — and a LaTeX plugin for WordPress. This seems a fair compromise between convenience and quality, but a compromise nonetheless.