This website has had a fair share of questions on the use of single versus double quotation marks. The most popular question on this topic is a good resource on their use in American and British English.
To summarize, American English mostly uses double quotes and reserves single quotes for specific use cases, while British English theoretically prefers single quotes, though this is not necessarily the case in practice.
However, I have noticed a pattern in the way some people use single and double quotes which is not mentioned in any of the style guides referenced in the question I linked to. Some people seem to use single quotes when quoting a single word or a phrase, and double quotes for anything longer than that. This would look like the following example.
While Alice said that this constitutes ‘proof’, Bob insists that “more evidence is needed before a conclusion can be confidently reached”.
I am not the only one to notice this use pattern. In his answer to the question I linked to above, a user called “mafu” notes that
I found that in practice single marks are commonly used for single words or short sentences while double marks are used to denote longer passages of text.
Is this a legitimate thing? Is there any style or grammar guide that recommends or accepts this?
I was trying to figure out the origin of this use pattern.
A user called “jbelacqua” explains in a comment that he/she does this because he/she feels that, since double quotes require more effort to input on a keyboard, they befit longer quotes which justify that effort.
Also, this use pattern might have been inspired by programming, as discussed in this question. However, that refers to quoting single versus multiple characters, so I’m not sure if that could have carried over to quoting single versus multiple words.