i guess there are two factors, character's intent and player's intent. I can imagine many number of instances in which a character may choose self inflicted death and a quick trip to the DR in favor of their current circumstances. Heck, Dakkru and the DR give us this loophole and we work with it.
Now, if a character does decide to off themselves because they have lost the will to live, then yes, one should assume that that character is perma-DED and should never be seen in the realm of the living ever again. If they do show up, then yes, we as players can assume that it was all an attention stunt, but play our characters accordingly.