The eTeX \scantokens command appears to work differently in LuaTeX than it does in eTeX, pdfTeX and XeTeX. Compiling the following test file with any engine other than LuaTeX performs \show+, which shows the character +, but LuaTeX skips this statement entirely.
\newlinechar=10 \catcode10=12
\endlinechar=13 \catcode13=5
\scantokens{^^J\show+}
\bye
This behaviour reminds me of how TeX does not look in a line after tokens of category code 5 (end-of-line), so at first I thought that the default category codes might be different in LuaTeX. This is why I added some redundant catcode assignments. Obviously, that didn't suffice.
