In the context of the exercise this is not a bug since it has no effect on the desired outcome, namely, the last names. So long as that result is as expected the exercise will pass.
You do raise a meaningful observation, and point out a potential future problem to solve when parsing such lists. Let that be a bug in your conscience so you will pursue it, further.
- Is it safe to assume that a comma-separated list will have space characters following every comma?
- Should said spaces be there would we be better to strip them later?
- When given a random list of names, what other characteristics would it be useful to investigate?
>>> authors = '''
Audre Lorde, William Carlos Williams, Gabriela Mistral,
Jean Toomer, An Qi, Walt Whitman, Shel Silverstein,
Carmen Boullosa, Kamala Suraiyya, Langston Hughes,
Gabriel García Márquez, Adrienne Rich, Nikki Giovanni
>>> print ([
x.split()[-1] for x in authors.split(',')
['Lorde', 'Williams', 'Mistral', 'Toomer', 'Qi', 'Whitman', 'Silverstein', 'Boullosa', 'Suraiyya', 'Hughes', 'Márquez', 'Rich', 'Giovanni']