My shell history is sure to show every use of ‘rsync <whatever>’ to be preceded by ‘rsync -n <whatever>’ to make sure I have the paths correct.

I get hit by that one. but, tbf Linux and BSD differ on the behaviour of cp -r with ./thing/ and ./thing -I found references to ./thing/. worked on both.

I also find the --include --exclude behaviour very confusing. does --include=* outweigh --exclude=thing and vice-versa and does this reset left to right?

That's why I have cpdup (https://github.com/DragonFlyBSD/cpdup) around on all systems I use. No need to worry about rsync's special syntax.