> whose troff dialect still underlined words with a string of literal ^H backspaces followed by underscores!
... which is still how roff tools do it today. Manual formatters still send, even today, TTY Model 37 style input from 1969 to the manual pager: underlining with BS and the underscore character, boldface with BS and overprinting, and bullet points formed by printing a plus sign over the letter "o"; all of which less/more/pg/most have to recognize (but ironically actually do not).
The relatively modern (1976!) capabilities of GNU groff were deliberately turned off at the turn of the 21st century.
By the way: File-based pipes were later created on a specific "pipe device", whose device number was configured by the /etc/config program and was not necessarily the root.