A long time ago I developed a way to append that text you’re talking about as an in house feature so we didn’t have to use that service whose name is escaping me right now. Probably spent two weeks making it cross browser. It was fairly simple at the end of the day and didn’t require any exploits to the clipboard api, just some really good assumptions to and timing it just right to flip some selection. The hard part was restoring the users original selection without making it obvious. I still hate that I did this.