Good points Kris -- I think I just had a knee-jerk reaction to the premise and didn't consider the rest of what you were saying. Like you, I have written some songs that are pretty autobiographical, and others that were pure fiction (although Bonnie is probably right that they always reflect something about the writer, even if the story is made up). The audience doesn't always know which is which, and I've sometimes been asked "is that true?" with an amused or faintly horrified tone, depending on the subject matter. I guess that if you're uncomfortable about the audience confusing the writer with the character, you could intro the song ahead of time to make it clear that it's not really about you in a literal sense. Or you could just leave them guessing, and let the chips fall where they may.

Audiences can be pretty funny about this stuff. One of the most telling examples of this (for me) was the reaction that met Randy Newman when he wrote "Short People" -- which was an obvious spoof on bigotry, but some actually took it as a serious attack. Randy Newman had a lot of those types of songs (the racial epithets in "Sail Away," promotion of nuclear attack in "Political Science," unkind references to the mentally retarded, etc.), and he tended to just float them out there with no explanation. I think this showed a certain courage on his part, and probably heightened the impact of the songs, but there's definitely a choice to be made -- especially if there's no escape door behind the stage.