NavList:

David Iwancio, you wrote:
"I'd wager there wasn't much in the way of formalized user research at the time, but even if "futzing around with tables of logarithms" was "familiar" to navigators it doesn't mean such processes were comfortable or used regularly."

Oh, but they were. This isn't a matter of speculation. We have ground-truth evidence in the logbooks and calculation notebooks that they kept. Logarithms were part of the daily work of any navigator ...any navigator with the most minimal level of experience.

Modern navigation enthusiasts sometimes make the colossal mistake of thinking that logarithms were some sort of advanced math, only accessible to smart, educated, mathematically-skilled navigators, probably because they're a topic only addressed in slightly advanced math classes today. This impression is wrong. Indeed, as I say, it's a colossal mistake. Any child could apply logarithms with minimal explanation.

Equally important to their regular use, navigators were not setting up generic problems which required the creative application of logarithms, they were learning efficient logarithmic algorithms crafted by people skilled in such crafting back home, on land, and handed to the navigator ready for use at sea. Any child? Even a lazy child could learn these logarithms. The only skill required was basic arithmetic: addition primarily, a little subtraction, and once in a while a simple multiplication or division. Logarithms were easy, well-known tools.

You continued:
"I get the impression that it was common in the Nineteenth Century for passing ships to share information they had on their current longitude with each other, and I find it interesting that they're sharing "longitude" and not simply "chronometer time." "

And where did you get this "impression"? And what if some pair of passing navigators did share "longitude" and not "chronometer time"? You have to engage in armchair speculation to draw any conclusion from that. Which, of course, you did next. You wrote,
"This implies that time sight calculations themselves were considered burdensome and were already in the 'I can do it if I must, but I'd rather not' category."

I must be very blunt here. That is nonsense. Maybe to get started you should read a bit of Hart's "Romance of Yachting" published in 1848 (a weird "blog-y" rambling book by an odd man --who is quite clearly not a genius). Not only does he describe how easy it is to calculate longitude using logarithms, and in too much detail, he even describes his wife yelling about cosecants and similar (meaning log cosecants, of course). Logarithms were common arithmetic familiar to any navigator in that era, and no ocean-going navigator would have sailed without them.

You added:
"Heck, user research by almanac offices in the middle of the Twentieth Century indicated that navigators were avoiding even using the moon's altitude, in part because of the extra steps involved in clearing it."

Step one: Almanac office publishes crappy tables for correcting Moon altitudes (I'm referring to the poorly designed and confusing tables in the back of the modern Nautical Almanac). Step two: Almanac office decides to investigate why its tables are not more popular. Step three: Almanac office blinds itself to possibility that current tables are awful and blames lazy navigators. Step four: rotten table are left in place and navigation descends into entropy...
Note to Future researchers: research on failed tools should not be left to creators of said tools.

You added:
"At any rate, no method of clearing lunar distances is going to save you from errors in the almanac."

This was a relatively minor issue by about 1775 and a negligible problem by about 1800. It's true that in much later decades some of the Moon tables were allowed to become stale. presumably because lunars were then obsolescent, but there was no problem updating the tables if demand required. For example when the first independent US nautical almanacs were published in the early 1850s, it was found that the American lunar tables (very nearly obsolete by then) were slightly superior to their British counterparts. Feather in the cap for Yankee Doodle, but of trivial navigational significance. And easily fixed by updating a few constants in the stale British tables.

You concluded:
"I noticed that the search for the wreck of the Endurance involved having to correct for errors in the moon's position in an almanac published as late as 1914."

Not relevant here. Lunar occultations operate at a level of accuracy about an order of magnitude higher than standard lunars (longitude by lunar distances). There was no significant problem with the moon's position in the almanacs with respect to lunar distances. To go an order of magnitude beyond (to properly interpret occultation events) with any accuracy requires modern tables and proper models of the mountains and valleys of the lunar limb.

Frank Reed