I’m afraid I don’t have any experiences with the xcard making the table less safe. I hope to bring something useful to the conversation nonetheless because I think safety mechanics are important and I’ve been thinking about them for some time.
I feel as if the issues with the xcard comes from whether the group is comfortable with using the card or not. If there’s a risk that the card doesn’t get used even though someone needs it, there is also the risk of people pushing harder and the risk that someone won’t object even though they feel like doing so.
Also you learn by doing. When you feel discomfort you might end up not using the card because it’s a new thing that you have yet to feel comfortable using. I believe it’s best to try it out early on, on minor things, to get a feel for how it works and affects the game and the group.
Feeling “this kinda ruins the fun for me” is a valid reason to use the xcard. That’s the whole point - you need to feel that any reason is valid. You should never have to motivate your use of the xcard even for yourself. Because that might lead you to think that you don’t have the right to use it, even though you really would benefit from it.
A very fitting metaphor came up on a thread on story games once:
A person said that the xcard is only supposed to be used in case of psychological harm, and said that it was just like a preference of food in comparison to an allergy: “I don’t like peanuts” compared to “I’m allergic to peanuts”. I happen to be allergic to certain foods and quickly realised that there is always a nuance to these things (with food as well as gaming experiences). I’m allergic to apples and nuts for example, but not to the extent that I die from eating them. My throat simply itches a whole lot. So, how bad a reaction is needed for me to use the x-card? I would definitely have a more pleasant meal if my throat didn’t start itching from it. So do I have the right to request “no nuts and raw apples”?
I argue that it doesn’t matter how bad a reaction you’re having because that question in itself is countering the card’s purpose. If you feel that “this ruins the experience for me” - then use the xcard if you want to change it. Simple as that. You get to trust your feelings however irrational.
I have used the xcard myself and I couldn’t really put my finger on why I felt the way I did. It was when we suggested that a PCs child was abused in school by his teacher (another PC) and we started discussing whether the child had said anything about it or not to his parent. We settled on that the child was abused but that it was all out in the open and that all parties knew about it. For me it was vital that we made this change, even though I couldn’t motivate even to myself why at that time.
I have also had one time when I didn’t use the card though I realised in hindsight that I should have done so. (It’s important to teach players that they can change their minds by the way.)
I think that it all comes down to the question whether people dare using it or not when they need to. If players would happen to push harder when the xcard is on the table, that’s not really an issue as long as the other players feel free to use the xcard when the game is moving close to their personal boundaries.
[a little self promotion to finish off with]
I have tackled this by making my own cards that are supposed to be used a lot (with an o-side to show approval and appreciation). https://www.drivethrurpg.com/product/279093/Traffic-Lights-ENG?cPath=32371_32906