If we take our idea of what's acceptable in professional English writing from Internet usage, we'll be falling down a deep, deep hole for a very long time. To Rooke's point, that tilde is a linguistic cheat, shorthand for emotion in situations where brevity and typing speed matter more than precision. Think of it as a one-character emoticon. And if we say this particular emoticon cheat is fair game, why not all the other emoticons? Rather than make thoughtful use of language to convey whether a person's dialogue is happy or sad or teasing, we could just stick :-) or :-( or :-P at the end of every other line. So much easier, right?
I'll be blunt: it makes for lazy writing. And worse yet, it makes for uninteresting writing.
Besides, you're kind of making my case for me. Your example shows the tilde (which looks a lot like the wave dash, but isn't) being used to indicate casual sarcasm. Then we have the wave dash (which looks a lot like the tilde, but isn't) being used to indicate bubbly joy. Oh, and also sometimes sarcasm. Oh, and also sometimes singing. So when a reader sees something squiggly at the end of a line, how are they supposed to interpret it? Is it uplift or put-down? Or pop hit? You might say the reader should figure it out from context, but in a translated VN, cultural context is an ocean away and linguistic context sits at the end of a long game of TL telephone. It's an iffy proposition at best.
I'll be blunt again: to leave squiggles at the end of a line is to leave a work partially untranslated. And in this case, the burden gets shifted onto the shoulders of an unprepared reader.