Slackware. As usual, takes the good bits out of both RedHat's and Debian's run-parts. It allows .{whatever} but ignores obvious, well-known suffixes like .bak etc.

From man run-parts: run-parts automatically skips files with certain suffixes that are generally associated with backup or extra files. Any file that ends in one of these will be silently ignored: ~ ^ , .bak .new .rpmsave, .rpmorig .rpmnew .swp

CentOS/Redhat or you could go full Unix with FreeBSD. Lots of other options too.

I switched to OS X in 2009. At the point I had been running Linux for 12 years, and GNU and Emacs on proprietary Unix for the 5 years before that.

I was a Linux user since 1997, but switched to OS X in 2009.