Dan/Branden -- don't forget that IBM had a flavor of the runoff family also at least by the early 1970s when I saw it.  In fact, I learned it before either the DEC ones for the PDP-10s which I saw next, and only after that the UNIX family.    We ran the IBM doc tool on TSS [often of 2741 style devices], and I think it ran on MTS.  Pre-laser printer days, although CS an XGP, it was only 200 dpi (and was on the PDP-10s).  So CMU computer center (IBM shop) even had a very high end printer with a golf ball (serial) output device that was in a locked room that was connected the 360 that they used to print 'special' letters on a fan folded paper that was super high quality and then run through the 'burster' to remove the edges and make it single sheets [Acceptance letters and other special things got printed on it by the computer center for the administration].   I don't remember much about that part of the process, other than the input/prep was from the IBM version of a runoff like program and as an operator, we had to learn to make it go and run things out on it as needed. But I do remember it was a PITA to output to that thing, but the SW also worked on a traditional 2741.  As a member of the computer staff I had access to the 2741 in my office (for APL work), but could set it up as a standard 2741 and type papers on it late at night.

On Wed, Jan 12, 2022 at 1:42 PM Dan Halbert <halbert@halwitz.org> wrote:
On 1/12/22 13:06, G. Branden Robinson wrote:
> Hi, Dan,
> At 2022-01-12T11:33:35-0500, Dan Cross wrote:
>> I have some questions about the earlier history.
>> I've been collecting a detailed narrative history not just of the *roff
>> _programs_ but also of the development on the language in the roff(7)
>> manual page.  Below I'll share a current chunk of it that is planned for
>> the next release (groff 1.23).  It has been heavily revised since
>> groff 1.22.4.  Many of my revisions have been motivated by accounts from
>> this list, from the "history of man pages" (more of a history of troff)
>> at manpages.bsd.lv, and the minnie TUHS archive.

I used RUNOFF on TOPS-10 in 1971, I think, and eventually also on TENEX
and TOPS-20. It probably was available earlier than that. Your history
is covering the Unix side, but there is also a pretty robust DEC side.
It was available on pretty much all the DEC machines.
https://en.wikipedia.org/wiki/TYPSET_and_RUNOFF has some mentions.

Dan H.