2) Were I to have accepted the brilliance of this use case, I'd only have been more interested in why 'pr didn't have the same behavior (which was my main gripe to begin with):
arc> (= speed 2)
arc> (prn "You are going " (if (> speed 100) "very ") "fast")
You are going nilfast
"You are going "
3) It was actually something I had already thought of and cast aside for the above reasons. (So it didn't even qualify as something "I'm not thinking of.") If aw was grasping for straws like I was, there probably wasn't much more point in talking about it.
4) It had upvotes too--at least one upvote at the time I first read it. Apparently, what I thought was common sense would be outnumbered.
5) I hadn't programmed in Arc that much yet. Maybe the upvoter(s) saw something there I didn't. At any rate, I'd probably be able to discuss the pros and cons better once I'd used Arc for a while.
6) I did say "I can't think of a single time," and this was a single example. I kinda decided to eat my words on account of that. :-p
Turns out (string:accum ...) is the use case I found that convinced me. The key point was that 'string wasn't consistent for symbols because it was too busy being consistent for lists.