Please keep in mind this is a rewards program text box, not a chat app. The program itself may be stupid, but I don't know any company that would allow these terms in internally visible recognition. My company uses manual review for recognition, but I would expect a call from my manager if I sent a public kudos "Great job fighting for union pay raises for the slave labor at our company"
If someone feels so strongly about the issue that they want to send someone a kudos using the specifi words "union pay raises for slave labour", that's definitely something I'd want to encourage as much as possible of, because it is a strong indication I'm doing something wrong as a leader.
You have to admit people won't use those words for fun in a professional environment. Those messages would be one of the most important signals uncovered by such a program.
I just don't get why you'd want to bury it.
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Though reading my own comment, it's clearly selection bias: leaders who encourage workers' open discussion of slave-like conditions would never institute slave-like conditions, and vice versa, I suppose.