I should preface this by saying that I myself am fairly young (a teenager) and speak primarily to other young people (while I may not know their exact age, it's safe to assume the other people I speak to are either teenagers themselves or adults slightly older than me who have not stated their age). I use Twitter as a platform to speak to Japanese people, and generally in replying to their posts I am talking about media, art, etc. and am not trying to say anything particularly meaningful. That said, which is the proper way to speak under these circumstances-- formally or informally? Most of these people are not ones with whom I'd spoken to privately before, but because of how communication online is facilitated I am a little shaky on whether speaking formally would come across as excessive or whether speaking informally would come off as rude. I see replies to Tweets in Japanese in both formal and informal form, so is it just a matter of choice?
Tl;dr use of formal/informal conjugation in online interactions in Japanese seems inconsistent to me, so I'm not sure which I should use.
In response to a post like "最近僕は描くことを考えるときに悲しくてなる", would it be better to reply "[name]さんの絵が本当に大好きだよ！" or "[name]さんの絵が本当に好きです。"