We don't have a local style guide. There are a few common practices that we inherit from a few different sources though:
Because we are using HTML (which is a format designed to be both human- and machine-readable), which gives specific meanings to certain kinds of markup, we benefit from recognising HTML semantics: italics for emphasis, bold for keywords and technical terms.
(All-caps is, online, widely considered to be SHOUTING. It's never necessary to shout for emphasis!)
We benefit from following general English style expectations: italics for Book and Movie Titles, quotation marks around “Song Names” and “words-used-as-words”. (Most often double quote marks, because single quote marks stand out less, visually. But this is a matter of personal taste and isn't generally edited.)
That said, italicising every mention of RPG books can sometimes feel really unnecessary, so often RPG book titles get no special formatting here. From experience that's fine — rarely is it unclear what's meant when the italics are left off.
RPG style has some influence: for example, it is common for D&D to use either title case for the Names of Magic Items and of Spells or italics for the names of magic items and of spells.
(This varies by D&D edition though, so you'll see people disagreeing about this. Generally, this shouldn't be changed through editing, because both are correct and switching the style doesn't make a post even a little bit easier to read. This is similar to AmE and BrE spellings: it's not appropriate to edit someone's spelling of “realise” to “realize” or vice versa, since it wasn't wrong in the first place. As a rule of thumb, we try to be consistent with the original author's spells and spelling conventions when doing an edit.
Specifically this edit to your question is probably what inspired your meta question. It was unnecessary and did not actually help the post at all, and you shouldn't take it as a sign that there is anything wrong with the style you had already been using. If you wanted to, it would be appropriate to reverse the edit's changes.)
code formatting should never be used for emphasis, highlighting, technical terms, or quoting. Its HTML-defined meaning is “this is input to a computer”, and we have italics for emphasis, bold for highlighting and technical terms, and quotation marks for quoting, so no need to misuse code formatting.
(The exception is tables, which we will often fake using non-inline code-block formatting to make the table columns align.) There used to be an exception for tables, but since it was made available we can use MathJax to lay out tables.
We do occasionally have posts that mention literal computer input in their paragraphs, and inline code formatting is appropriate for those. We save it for that use.
Because it's standard English practice and how our formatting system is set up, large blocks of quotation go in blockquote formatting, which means starting each paragraph of the quote with a
Book/page citation style varies in English and is only defined by various academic style manuals, so we don't naturally inherit anything in particular. Go with whatever is familiar, clear, and has a verbosity or brevity that suits the particular position of the citation.
It helps sometimes to divide a post into sections with headers. Never use bold for these section titles! Such “fake” headers are invisible to machine-reading and can seriously impair our site's accessibility to people who use assistance programs. Instead, use the header formatting options provided to create semantic section headers. They will look better in a visual browser, too.
People will sometimes use horizontal lines to break up sections of a post too, when a separate title for the section doesn't make sense. It's easy to overuse them, but sometimes the judicious use of a horizontal rule makes a significant improvement in how the post reads.
Our list formatting input is unfortunately American-centric in its design: it doesn't recognise
1.) style lists (yet!), so list numbers always have to be written
1. like that, followed by a period. Otherwise, they don't render into into an HTML list at all.
In practical terms, what these influences combine and add up to, in terms of a “common denominator” of how to format a post and have it be understood and not look “random” is:
- When in doubt, less is more so just leave out a piece of inline formatting when you're unsure about it.
- Standard emphasis is to use italics.
- Put proper nouns in Title Case, in general, especially if there is a need to make it clear that they are a Name and not just words.
- Powers are often proper nouns (but not always), so Title Case is often used and works fine. Sometimes it's desired to make them stand out though, and in that case use keyword formatting to make it clear it's a special term.
- Technical terms, similarly, often don't need any formatting, but when they do need to be formatted so that they're unambiguously seen as a technical term, use technical term formatting.
- Use double quotation marks by default. Single will sometimes be useful though.
- Use Markdown's formatting features for outside-of-paragraph formatting whenever possible, to give a post visible and semantic structure that matches the structure of its existing intended meaning.
This looks like a big pile of rules, but what I wrote at the beginning is still true: we don't have a local style guide. We have various influences — English writing conventions, our Markdown formatting system's design, HTML's structural semantics, the styles that appear in RPG books and academic citation guides — that people are familiar with or that the human and machine consumers of our pages expect, so looking at those helps figure out good style practices. Seeking the lowest common denominator of all the styles that our readers understand is the most effective way to format a post.
In the end, clarity is the foremost concern, so what's clear and unambiguous is always best. And when a post is already clear, it shouldn't be edited just to make it different without any clarity improvement.