IMHO the persona matters.

I hope the echo of other's remarks is not too loud. When behavior, habits, addictions etc make a musician or artist unpleasant, or gives them a disagreeable character in the opinion of the listener, then yes the character matters. If this character is only self-destructive, it is not as important (to me) as when it's destructive of others and their surroundings. Taking into account the human qualities of forgiveness and temptation, the parameters of this are quite variable. Nonetheless, the PERSONA matters to the delivery of a song. (Example: Madonna singing American Pie, see another thread re that.) I might also point out that some very important and good songs have been written by people with qualities many find disagreeable, because it is that disagreeable experience/quality which gives the writer the ability/experience/knowledge to write the song in the first place.

Peace, MoohTooh (Mooh from elsewhere).