This is copied from Unchanged rows are deleted. Changes are marked by <del/> and <ins/>. These are some of my disagreements. (Also, Uriel: Why didn’t you put whitespace where it belongs in front of an opening parenthesis? And what about those pesky full stops, or rather the inconsistency thereof?)

Harmful thingsLess harmful alternatives
SGML, XML, YAML.JSON, CSV, ndb(6), plain(UTF-8) text, S-expressions.
Bash, tcsh, zsh.rc, OpenBSD's pdksh, ash/dash, depending on the use case execline.
GNU Coreutils.Plan 9 from User Space, skaware.
GNU info.Man pages, other documents set using troff or TeX.
GCC.8c, tcc, cproc.
Glib.libc (see above), p9p's C libraries, skalib.
Apache, lighttpd.thttpd, OpenBSD's fork of apache 1.3, nginx, httpd, or best of all: don't use HTTP.
SVGPS(PostScript), pic
PDFPS(PostScript), DjVu, PDF.