Why does python use unconventional triple-quotation marks for comments?

Python doesn’t use triple quotation marks for comments. Comments use the hash (a.k.a. pound) character:

# this is a comment

The triple quote thing is a doc string, and, unlike a comment, is actually available as a real string to the program:

>>> def bla():
...     """Print the answer"""
...     print 42
...
>>> bla.__doc__
'Print the answer'
>>> help(bla)
Help on function bla in module __main__:

bla()
    Print the answer

It’s not strictly required to use triple quotes, as long as it’s a string. Using """ is just a convention (and has the advantage of being multiline).