Agreed. A linkbegging ban is sufficiently unusual that separating the intentional violations from the "I just assumed it would be like other boards" people might reduce the "sucker born every minute... and you have to re-explain things to each of them" problem.
The problem with having unusual rules is that no one has the time to go look through each and every site's list. Sure, it takes only a little time for one board, but who comments on only one board? And 99.5% of the rules are common sense anyway: Don't flame, don't cuss up a storm, don't pick fights and keep them going for pages and pages, etc. Not hard to follow those without reading word 1 of any site's rule list. So you'd have to look hard through the endless sea of same to find each site's quirks.