Level of Distractibility: Who cares? = *. Some people will be distracted from your meaning = **. Many people will be distracted from your meaning = ***.
Question: When do you double the final "l" in the word "cancel"?
Answer: A little known American spelling rule is that if the accent falls on the first syllable, you retain the single final consonant: can'cel, can'celed, can'celing. If the accent falls on a later syllable, you double the final consonant: cancella'tion.
"Can'cel"; "can'celed"; "can'celing"; "cancel'lation": The first three have the accent on the first syllable; therefore, a single "l." The last item has the accent on the third syllable, so the "l" is doubled.
Rating of Distractibility: (*) I don't think most people know this American spelling rule and it gets mixed up with the British habit of doubling final consonants for almost everything. Therefore, I don't think many people will even notice whether you follow the rule. In fact, to me, the single "l" in "canceling" and "canceled" does not look right.