Not really. Contributing factors:

• I have a reasonably consistent internal single/double quote rule, which is to use single quotes unless a string is more complicated to express with them (for example, it contains "\n" or variables). A theory here is that single quotes are a cue to the reader that the rest of the string isn't interesting/magical, and particularly that it contains no variables, so they can ignore it when tracing a variable. This is a very fuzzy motivation and there are probably plenty of strings that I'd write differently on different days. It also leads to using single quotes or double quotes inside strings (to demarcate values) inconsistently, as I'll sometimes just use whichever one doesn't need to be escaped. As we're pht()'ing the codebase, there's less need for magical strings, so this is getting slightly more consistent. (We could use just one quote style consistently, but this would make some strings dramatically less readable, no matter which style was chosen.)
• I used to use backticks around commands a lot but have sort of moved away from it. I think it's a little weird and partly just laziness because they never need to be quoted. I'm not really sure if this practice is useful ("backticks delimit commands"), lazy (backticks don't need to be quoted) or just bizarre, or some mixture of the three. I have a fair number of weird idiosyncrasies that I've mostly tried to move away from. For example, I used to indent all the code in every file under the theory that <?php creates a scope. Technically arguably, but not very pragmatic.
• I am having a pretty fuzzy brain day today.

I'll make these consistent. My reworded exception is probably not very readable anyway because you end up with dot-quote-dot at the end, which is difficult to scan. A better phrasing of this would probably be:

...use:

  $ arc browse .