Merrill Perlman has an edifying rundown of the chaotic situation with regard to single or double consonants before suffixes in English. After laying out what might laughably be called the rules, she says:
“Worship(p)er” is a victim of the confusion that can arise when there are too many “rules.” Generally, the final consonant is not doubled if the last syllable is not accented (in American English, that is), as in “listen/listener.” That means “worshiper” should be a no-brainer. For whatever reason, though, as Bryan A. Garner says in Garner’s Modern English Usage, the single “p” never caught on in American English; the double “p” appears three times as often as the single.
Let’s move to the “l” problem, which is where British and American English diverge the most. someone is a “jeweller” there and a “jeweler” here; a legal document is “initialled” there and “initialed” here. And a favorite TV show is “cancelled” there and “canceled” here. Most words that end in “l” add a second one before many suffixes that begin with vowels.
In The New Yorker and Chicago style, the show is “cancelled.” Just to play with your head more, everyone uses “cancellation.” And though many dictionaries, The New York Times, The New Yorker, and the Moon prefer “tranquillity,” many people seem to prefer “tranquility.”
The important thing to remember, as we say so often, is that sometimes things are not necessarily “right” or “wrong,” just a matter of choice or style. With doubled consonants before a suffix, the answer sometimes is simply “it depends.” Or, maybe, you could look it up.
An admirable conclusion. Just to repeat for emphasis: sometimes things are not necessarily “right” or “wrong,” just a matter of choice or style. Life would be so much more pleasant if people would keep that in mind.