Note: The topic I linked actually agrees with the mods decision, so I withdraw the proposal.
I have seen that some users have written a comment under their questions to make it clear they were about the current Challenge Week, which is about Weapons.
My proposal is simple and is valid for future Challenges too: let's use a tag for the questions regarding the challenge, something like weapons-challenge-week or something similar.
This way you can easily find the related questions and when the week is over, it's easier to retrieve them and see which ones to consider for the draw, without looking at each one to see if the comment was provided.
When I proposed Sklivvz this in a comment, he replied that such tags would be Meta-Tags (I invite him and also other mods to post), but honestly I don't think they'd create harm in this case.
In order to successfully question this view, I decided to bring forward the Challenge Week topic on the Philosophy SE, where such tags are suggested by a CHAOS team member, so it does make this a reasonable proposal, in my view.