Style guides mention two conventions for quote marks which appear to be in conflict.
* quotes (within quotes ...) within quotes/dialogue show nested quotations by alternating between single and double quote marks
* non-literal expressions may be enclosed in quote marks but single or double quote marks are used to distinguish between different types of meanings. Single quotes are used for, say, metaphorical expressions which are suggestive the author's intended meaning. Double quotes (aka scare quotes) are used for irony when the intended meaning is the opposite of the literal meaning of the expression.
This apparent contradiction would rarely cause problems in formal writing. That would not include quotes of others' sarcasm very often.
However, this is causing a dilemma for me with my WIP. It contains a lot of dialogue from one character who's both pretentious and cynical. Within dialogue, I will need to distinguish between pretentious metaphors (single quotes) and ironic sarcasm (double quotes). And yes, for those who wondered, WIP is semi-autobiographical.
I think I know the answer. The alternating of single and double quote marks only applies to quotations, not expressions. This should not cause confusion for readers because quote marked expression should never be longer than a few words.
How do others handle this? Can anyone identify examples of how dead-tree authors of fiction have handled it?