Ok then, here's my constructive criticism: Don't make an 'OS' that's a replacement of 3 files that do virtually nothing. How's that?
Pretty awful. Here's my constructive criticism on your constructive criticism:
There's two components of constructive criticism: the "criticism" bit, where you tell someone what's not so great, and the "constructive" bit, where you tell them how it could be more great next time. Now, obviously you've got the first bit down to a tee, but you're rather lacking in how they could improve it.
The issues with this is firstly people don't learn to improve if you don't help them, and secondly it's darn depressing if someone says "this sucks, do better". CC has had an emphasis on getting people started on programming for a long time, if the forums can't satisfy this who can? And yes, it gets frustrating at times.
So, in short, I think the biggest thing you could change would just be adding a couple of sentences at the end saying some possible improvements. Maybe point them towards the PIL book, so they can learn a little more Lua. Maybe suggest they have a read of Lyqyd's fantastic guide on formatting code (though criticising formatting is always a little blughr). Personally, I'd recommend writing a couple of other programs to go along with it - such as a small game or something. Or just not writing an OS at all :P.
Of course, the best thing about constructive criticism is you get the joy of saying "you're wrong", while still pretending you're being useful.