Is it advisable to replace 'self' with '_' or 'I' or something shorter?

[Jonathan P.]

I agree with the fact that explicit use of self is good
for code readability, however it tends to make code lines
too long.  Since 'self' is just a convention, I wonder if
people out there have tried replacing it with a one-character
equivalent without encountering any problems.

I was thinking of using '_' ('I' is a distant second
choice) instead of self.  Comments?