Is there a way to write subscript on EL&U?
Yes. Use the
In the series x1, x2, x3, ⋯ xn, we see …
There are corresponding
And for certain, specialized uses, there are specific Unicode characters you might find useful¹.
¹ Such as the superscript numerals
More Formatting Options
I have yet to find one source that completely describes all the markdown and HTML features StackExchange supports, but these four together seem to cover the bases:
- Editing help: list of all the standard Markdown features available in "plain text" editing.
- Canonical Markdown reference (external): note that SE's Markdown may deviate from this spec in order to tailor the syntax for its own purposes.
- HTML tags supported by SE: These are HTML tags, over-and-above the formatting features offered by Markdown, which SE supports. The
<sup>tags mentioned above fall into this category.
- Magic links supported in comments: These are handy shortcuts for use in comments which make it easier to say common things, like "questions about the site belong on [Meta]", which will automagically convert the bracketed text to a link to that specific stack's meta.
Then there are small details like ```-style Markdown code blocks, which I'm not sure are comprehensively collected anywhere. If anyone does know of a single, central, consolidated, comprehensive, and authoritative reference, add a comment and I'll update this answer.