I literally blog with raw SGML. Each post comes with a handful per post ENTITYs for that post's common abbreviations and links. Unlike inopinatus's comment, I do keep up with "modern" standards, which is why my posts conform to the "ISO/IEC 15445:2000//DTD HyperText Markup Language//EN" doctype, the latest HTML standard approved by the ISO.
Blog content is assembled via various SGML entities includes into a prehtml file of "-//ISO-HTML User's Guide//DTD ISO-HTML Preparation//EN" doctype per ISO 15445:2000 recommendations[0]. This is all processed with osgmlnorm through a somewhat simple Makefile to generate the resulting HTML files.
[0] https://rogerprice.org/15445/UG.html#DOCPREP