As the miscreant that posted the "regurgitated train" gag, I am sympathetic to the desire to keep the site from descending into chaos. I also understand that any rule proposed will be pushed to its limits by jokesters on one hand and parochial school teachers ready to rap knuckles with yardsticks on the other. hand.)
While every project can improve in some way, I have no complaints about the way people manage this site. Given the popularity of foolish things like helicopter mace I also think it would be a mistake to ignore that people need a break now and then.
It would not be good to have joke answers crowd out legitimate responses to serious questions. In the specific case of "train", the question was about a biplane photoshopped onto a WW2 rail gun, hardly serious. Also with the gag deleted there are now zero answers, so no crowding out. I think it is reasonable to ask where is the harm? If you are being consistent you should really delete the question. (I am not advocating that)
I think it will be difficult to make one simple rule that works everywhere. I think any solution that will give both sides something is going to require a judgement call, so I understand any inclination to ignore the whole thing and leave things as they are. However, if the No Fun Rule is to be relaxed I would suggest:
- gags in comments are ok anytime, as ymb1 suggests, though I disagree that photos are well handled
- gags in answers are ok if there is no harm, as I think was the case for "train"
- gags in answers will be deleted immediately if there is harm to serious questions, but I think calculating integrals don't lend themselves to jokes so this might not be common
- gag questions and harmless gags in answers will be left up for a week as TomMcW suggests, but left up if they are really popular. If you are against fun, letting jokesters earn reputation may represent a perverse incentive but it is somewhat balanced by the threat of impending deletion if the community doesn't really love the gag.
There would need to be some discussion about what constitutes harm and how much love lets a gag survive. There would also have to be some communication about what is allowed, to keep the line judges from being outraged.
The good thing about making it a judgement call is that if things get out of hand you can get more aggressive with the deletions without a big conference to change rules.