I've been thinking about this for quite some time now. I've seen 2-3 variations of the template comment in active use. All of them link to the homework policy we have in meta. But this is the template comment I commonly use instead:
Hi %name%, welcome to Chem.SE! We have a homework policy that requires you to show your efforts on this problem. What did you try? Where did you get stuck? Please add this to your question. Thanks!
See? It doesn't link the user to any policy. It just gives them a tl;dr summary of that policy.
I think this has the benefit that users are more likely to read and quickly understand this short summary, and act upon it quickly as well. This might increase user retention rate. If we link them to a homework policy, they might just skip reading it and never come back. They might tell their friends that "Chem.SE has a weird lengthy homework policy...unfriendly site" (of course, that's not what I think though :P)
I am not saying that we should try to retain all users. Many users are non-cooperative and retaining them does more harm than good. They may leave us as happily as we bid them good bye. But, there are also good-intentioned users and we should attempt to retain them. English might not be their first language. How can they be expected to read a lengthy document? Or, they might be users who think: "ok, i'll read this long document by tomorrow and then edit my post". But, when they return tomorrow, they observe "5 downvotes and question put on hold! Unfriendly site, better leave this place..."
So what are everyone's views here on what our default template should be? Again, I neither can nor am I trying to enforce any rules on anyone. If you're using some template of your own, feel free to continue to do so. But I am hoping to reach some consensus on what the best template can be, with input from everyone.
EDIT: Martin quickly pointed out in his long answer that the very mention of the word "homework" can lead to a debate with the OP as to what is homework and what is not, which is very correct. So, as per his suggestion, here's a better comment template:
Hi %name%, welcome to Chem.SE! We have a policy that requires you to show your efforts on this problem. What did you try? Where did you get stuck? Please add this to your question. Thanks!
^-- no mention of the word "homework" there.