Generally Chicago Manual of Style - 17th edition (CMOS) is used as of July 2018, but divergence is allowed depending on the contribution and context. For example if we have a British contribution using large amounts of British styling and/or spelling. The objective of using CMOS is for consistency for the reader across the site.
http://www.chicagomanualofstyle.org/book/ed17/frontmatter/toc.html
As ever the golden rule is consistency.
- Comma after e.g., but not always depends on context.