こと (Must Do) Confusion

Question

I often see こと used when listing rules:

1. 冷蔵庫の物は勝手に食べないこと→ Don’t eat my things from the fridge

2. トイレ掃除は毎日交代ですること→ Clean the bathroom every day by turns

The above examples come from a written list of rules a character in a drama made for his roomate to follow, which is where my question comes in:

Is this こと really appropriate on such a casual scale? My impression was that this structure is only used when outlining formal written rules. Or are all written commands/rules (regardless of formality) presented in this format? Also, for clarification this, こと is never used in spoken language, right?

But then I came across an example of what seems to be the same grammar (but used in spoken language?) from this video:

「見ないこと、見ないこと」→ Don't look, don't look

Can someone explain why こと is used in this instance? I have a hunch that the reason has something to with the fact that he's listing "steps/rules" in the video (but then again none of the other steps use こと, so maybe not), but I would really appreciate an explanation.

Answer 1

Yes this type of こと looks more or less formal and serious. It makes these sentence look like an "official rule of the room/family." I don't think it's overly formal nor grandiose. Other options include "食べないでください" (sounds more like a polite personal request) "食べないで!" (a casual request), and "食べるな!" (sounds like the poster was upset).

Using こと in speech is not very common, but it's okay when you want to seriously ban or enforce something. Parents and teachers sometimes use this pattern. (I don't think the guy in your video is a good example, though. He is just reciting the rule to concentrate.)