I think regular check-in is an important part of running a smooth session in general--whether it's for safety or for narrative resonance or for having fun or even just to decide when to take a break or stop for the night.
I'm not expressing that because the tools are a shorthand for direct communication clearly they are a panacea, I am expressing that the abuse of the tools that was described does not look like a tool problem, it looks like a more specific problem with the behavior of the people who did those things. You can't replace caring how people feel and paying attention to that with a pithy rule system nor can you replace feedback from people who are uncomfortable--on the spot, in private, or wherever--with an external tool-suite. These things do not offload the responsibility of diligence, but neither are they supposed to.
I'm not trying to correct anyone on their own needs, but I'm wondering how useful the framework that many or most of these tools are bad because some people misuse them or because they aren't one-size fits all really is. I completely understand that these tools will not support everyone in every situation of need and I personally find the x-card in particular far less useful than other approaches. I'm not looking to dispute any of that, but I'm not seeing where this particular approach leads to.
I suppose we can launch in a slightly different direction and express which tools are best for which sorts of issues and groups, but beyond that I'm in a more optimistic version of the end of the thread--there really isn't a way to design around people engaging recklessly or harmfully, but there are ways to prepare players acting in good faith for issues they might not anticipate. I think my favorite approach is definitely games that describe several of these tools and the reasons for using them rather than dropping one or even several into place as though they're part of the system of the rules rather than part of the more nebulous social contract of sitting down to enjoy this thing together.