The ones I've read are relatively straightforward Lua, though.

Some shootout programs look really hairy compared to normal code in their language. (The "optimized Haskell" shootout programs were, at one point, though I haven't followed it for a while.) With Lua / LuaJIT, that doesn't seem to be the case.

Besides, Mike Pall is using some of the shootout benchmarks to tune LuaJIT, so it's not surprising he has many of the top submissions.

It isn't a matter of being surprised that Mike Pall has contributed programs, more a statement of the obvious lest we forget.

Mike Pall is kind-of a good programmer, and that may well effect how the programs perform.

I think it has more to do with how his runtime performs. :)

Tuning Lua code really isn't that hard, the language is tiny and has both semantics and performance characteristics that are easy to reason about accurately.

There's a good sample chapter from _Lua Programming Gems_ on Lua performance tuning (http://www.lua.org/gems/sample.pdf), FWIW. That and a good profiler will get you far.