For some people, the exact birth and death year is not know with precision, and sometimes a sources mentions that they were already dead by some date. In that case, I mark the date as "after". (e.g. if someone was mentioned as deceased in 1844, I set the death date as "before 1844"). Same if the last mention of a person in a source indicates that he/she was still alive ("after 1844" in this case).
However, when viewing the family tree for those people, only the year appears, with not indication that this is a "before" or "after date" (e.g. for that person, you would see "(n. - 1844)"). This is error-inducing, as one might think that person died that year when in fact might have died years before.
I think something like "(n. - bef.1844)" or "(n. - <1844)" would make things more clear.