I'm not really buying it, to be honest. There's a wealth of research that confirms friendship is the key to a successful relationship. If you've been friends with someone for years and if you truly value your friendship with them, you're going to work hard to make it work if that relationship does indeed roll into sexier territory. You've already been best friends, so why wouldn't you want to work at it? Too many people now just throw themselves at the first person who gratifies them sexually, and then when the tits drop we turn around and wonder why the divorce rate is pretty close 50 percent across the board, lol.I think it comes from the fact that some people view characters a certain way and when they enter a fanbase and see characters they see as platonic being shipped as something other than friends so popularly it gets annoying seeing it everywhere. I remember with my first experiences how weird it was to see characters I never thought of as couples being shipped so hard. I think what Deathstroke means is that they value Jill and Chris's relationship as friends and if they became a couple they lose something that made them great friends without being romantic but hey I could totally just be pulling this out of my ass take what you will from this ┐(‘~`;)┌
I think it's inherently cheaper to say 'I don't want to try this because it might ruin my relationship with you'. If you're willing to pass on someone who is very well a potential mate, who has bent over backwards for you and risked their own life for your welfare (and in fact was willing to risk a lot of people's lives for your welfare) just because you're scared it might not work out.. I think that's pretty sad, tbh.
This is my inherent problem with the suggestion that romance cheapens friendship and as an extension, the suggestion that Chris/Jill is somehow less valid than pairings where characters haven't even met/have no relationship or are in some cases even arch enemies. I can't think of another pairing who'd be more stable than Chris and Jill. And if a stable relationship is a cheap and degrading one then, well, fml.