I know there has already been a lot of discussion on this site regarding how to arrange the punctuation when a sentence ends with a quote within a quote.
1) "'...the end of a sentence'."
2) "'...the end of a sentence.'"
And in most cases, it seems like people have come to the conclusion that neither option is really correct or incorrect and it's all based on preference, US vs. UK English, etc. I personally tend to prefer Method 1 because I feel like having the inner and outer quotes 'split' by the period makes things easier to read.
But I've noticed something peculiar recently. I beta read for an indie author friend and she tends to prefer Method 2, only she goes through the completed manuscript and inserts a small space between the inner and outer quotes to make things a little less crowded. It looks a little more similar to Method 1, but the structure is still period > inner quote > outer quote. However, if the sentence ends in a question mark, she uses Method 1, so the structure is inner quote > question mark > outer quote, or "'...question'?"
I've noticed the same phenomenon in the book I'm currently reading, a new release in a popular series from a big-time author. Quotes-within-quotes ending in a period have the period inside both the single and double quotation marks, and those ending with question marks have the ending puncutation sandwiched between the quotes.
In both cases, it seems like the authors are using Method 2, except in the case of question marks. Is there some sort of rule that explains this? Why do it one way for certain punctuation and a different way for something else?