See say How about limit new accounts? - #15 by Mateusz_Konieczny
It would block anyone trying to map forest/lake/road/multiple buildings as their initial edits, what seems undesirable to me
Adding 6 square buildings is already: 6 * 4 = 24 nodes, 6 new ways - for 30 map changes in total. And it is a reasonable edit in the first day of mapping.
I would go with limit like 1000 changes per day for new accounts, later upgraded up to 50000 per day with bot-flagged accounts having no limit. Which should already put some limits on vandal scripts without harming true users.
But even 1000 changes per day would likely cause problems for say people attending workshops about OSM mapping.
(emphasis added)
Though it clearly underestimated scale of even initial edits some attempt to make.
I am pretty sure that I also mentioned HOT editing elsewhere (many new users adding very large volume of buildings) as the most likely false positive and that it would not be false positive in case of very low quality data at large volume. But not sure is it on github or some volatile location.