I wasn't implying anything. Maybe "restrict" isn't the best word choice, but I was just pointing out that lui means his, ei means her, and sale can mean either his or her, depending on context. This means that sale can be used instead of lui or ei in those two sentences I gave as examples.
WestleyT's question is perfectly valid. I didn't answer it because I simply don't know with certainty which is more common. But, to throw my two cents, I would say that său/sa/săi/sale feel more formal and old-school at the same time; plus they are ambiguous without a context. I prefer using lui/ei instead.
You are almost right.
- său/sa/săi/sale* - mostly written language and for formal purposes (school, media, correspondence, literature etc). It is more common in the south (ex. Bucharest).
lui/ei - both written and spoken language. It is much more common and preferred in the Moldavian part of Romania and Republic of Moldova.
But there are plenty of contexts where the 1st form is used and preferred (both formal and informal).