Today there is no difference between using single or double quotes (or [...] or `...`). They will all be interpreted as quotes defining a search and not a literal match.
But just as stalwar1 points out - it is a bug. Fixing it was more complicated than we thought, so it has still not been fixed. But we are working on it right now and my guess is that we will have it fixed soon.
In the future it will work like this:
Double quotes: Case insensitive search where * and ? are interpreted as wildcards
Single quotes: Case sensitive string match where *, ?, =, > and ~ all are treated as any characters
Yeah this post is what confused me. So you are saying 'C*' is working because it is a bug? Ideally this won't work? because this post is from 2015 and I would imagine a bug in 2015 would be fixed by now.