The rule says, “No vehicles in the park”

In my mind the rule would obviously have related list of reasonable exceptions filed away somewhere; the simplicity of the rule is to improve the effectiveness of preventing the common case violation of regular people driving their cars through the park, causing damage and impacting the people using the park for its intended purpose.

In my opinion almost all of the examples provided were either obviously not applicable or were perfectly reasonable exceptions (and I don't think exceptions violate a rule).

* means of carrying or transporting something (planes, trains, and other vehicles) such as a) motor vehicle or b) a piece of mechanized equipment - Websters Online Dictionary

* 1) any means in or by which someone travels or something is carried or conveyed; a means of conveyance or transport: a motor vehicle; space vehicles. 2) conveyance moving on wheels, runners, tracks, or the like, as a cart, sled, automobile, or tractor. - dictionary.com

* a machine, usually with wheels and an engine, used for transporting people or goods, especially on land - Cambridge Dictionary

Any of these definitions could have been applied successfully to the series of questions on the website without ambiguity (edit: without ambiguity, but each would have led to different sets of conclusions). Which is to say, the entire point of the excercise reduces down to finding out which definition of the word someone is working from. This is only a problem if we're dealing with something that can't be defined, or something that we refuse to define.

Example #1: I didn't poison Joe. I was out of town when it happened.

Example #2: I poisoned Joe. He had been sentenced to death, and my job is prison executioner. That's why I injected him with poison.

The second example is an affirmative defense. A murder occurred, but it was not illegal because it was authorized by the state.

I have a feeling that lawyers who took this quiz were more likely to answer yes for the ambulance and police car, but nonlawyers would answer no. That's because most people were answering the question "would they get in trouble?" But lawyers might have been thinking "is there a valid defense to a violation that actually did occur?"

In your example, calling for the death penalty isn't advocating for violence because executing someone in the justice system is legally permissible (let's not get into ethics or morality). The Reddit rule is generally understood to cover only illegal violence.

Other definitions include an agent of transmission (e.g. for and infection) and a medium though which something is displayed (dance is the vehicle for my creativity). Would have been interesting to see the different definitions exploited vs more strained classification of shoes or skates or whatnot as vehicles.

Having rules against advocating for violence means that you want to prohibit such calls (otherwise you would have written down such exceptions and admit that calling for violence is sometimes OK).

Let me put it this way: what Reddit secretly wants is not standing up against advocating for violence, but avoiding the reputation risk that might happen if there exist to many post that advocate for violence in a way that causes an outcry.

In other words: the hidden problem is rather Reddit's "secret" agenda behind the rules.