If you have a way to recreate it, can you debug it? I’m thinking this is the location
https://github.com/discourse/discourse/blob/be3a5a56ccc284b352aa65080fc6b955f73cc72a/vendor/assets/javascripts/virtual-dom.js#L874-L889
text would be the propname you want to stop the debugger on. I wonder if trying to set it via element['text'] = value is not happy with the older version of safari.