Bikeshedding like this is useful as a team efficiency metric.
If you can't get quickly to an agreement about such a thing, or if the members of the team that didn't get their way actively rebel (or worse sabotage), you are working with a team of divas.
(note: of course developers whinge, as long as you stick with the team decisions once their are made, whinge all you want)
Well that's the point. Feed the team with a trivial problem to see how they react.
A well working team will probably do as you say - volunteer an individual to write the rule in an email and follow it from there on.
If you going to introduce changes in a team, like for example introducing Agile (the proper way) or you are starting a new project, you want to quickly gauge the team dynamic, and that's a good exercise.
If you can't get quickly to an agreement about such a thing, or if the members of the team that didn't get their way actively rebel (or worse sabotage), you are working with a team of divas.
(note: of course developers whinge, as long as you stick with the team decisions once their are made, whinge all you want)