sometimes it _is_ valid. In SnabbSwitch, once I found a single local
variable missing had a 6% impact in the number of packets processed
Right, that is a perfect case for micro optimisations, because throughput is key, but that doesn't (IMO) generalise out to "always do this".
/me shrugs, it's not like I'm expecting anyone to change their preferred Lua style because of me, I just wanted to at least put some numbers behind the actual overheads, in case people are just blindly copying the style without knowing why :)