After reviewing the last few pages, the best I can come up with is that undue sensitivity was either present or perceived in the exchange about where that image from Facebook came from. So maybe when Serza said "Why are you being like this" Stormy may have thought something like "I can't even tease here anymore without people getting all serious" and that was that. I don't know if Serza was actually getting upset over the lack of specificity about Stormy's Facebook feed contents, or whether conveying that was the intent, but that's the best I could come up with.
Seems trivial at best, but as with when speculating about Beren's departure, these things can always be the final straw that wouldn't otherwise themselves be departure-worthy.
I don't know what the glory days of DQ were like so I can't share the sense of loss you folks have, but since this is literally the only reason I have BSN on my bookmarks toolbar I hope it's neither a trend nor a permanent thing.