There’s actually another problematic “feature” with the Hide my public profile and presence features profile setting which currently makes it (unintentionally, I believe) much harder to message someone who chooses that setting, since it removes the message button from user cards:
Mind there’s a separate setting for disabling messages, but this is being caused by the Hide my public profile and presence features one. I don’t think one wanting to hide profile and/or presence means necessarily that one doesn’t want to receive messages (as easily, that is). Anyway, sorry for bringing this off-topic.
Back on topic and, for what’s worth, we are using this plugin (which we 
) on a fairly active forum (~140 concurrent online) and look forward for some optimizations. I’m not a Rubyist, but happy to help in any other way I can (feedback, benchmarks, etc).