On every social media platform I've ever been on, the worst DM conversations start off with someone writing nothing but, "Hi".

What a simple "Hi" means is that they're trying to build towards something.

@atomicpoet True. It’s also not limited to social media. Whenever anyone messages me at work with nothing but a “Hi”, I brace myself because it means I’m about to get busy with something that was not on my agenda.
@atomicpoet I always prefer when someone sends the Hi, He/She attaches the intended message. We have no time to Hi and Hey

@atomicpoet Very true! I usually get this on Instagram, Telegram & now Twitter.

It’s people trying to sell me crypto, a quick-get-rich scheme, or porn.

I think Telelgram (to their credit) is cracking down on this, so it is no longer an issue there, but I have seen a spike of this upon Twitter after Elon Musk took over.

I have not had that upon Mastodon thankfully.

@atomicpoet I 100% never reply to a DM that reads only "hi".

@atomicpoet That sort of thing is so annoying (in DMs as well as IM) that there's a whole website dedicated to it.

https://nohello.net/

no hello

please don't say just hello in chat

@atomicpoet yes, they might try to build towards something but that requires you to invest (time, attention, mental capacity) before you know what it is. Could be worth it, could not be. https://aka.ms/nohello is one way to handle it. This is a very "western" approach to this though. In other cultures the waiting after a "hi" can also be intended to show respect by not running in with the door.
As always, context and (existing?) relationship/contact matters A LOT.
nohello

@atomicpoet

Maybe preferred salutation Alexander Graham Bell had envisioned for the telephone is how we should start DMs here. Just a idea  

@atomicpoet Hi are you He Man In disguise 🤪

@atomicpoet

Yeah no. It's creepy. Why should anyone engage in a private conversation with someone they just followed back? That's usually when I get 'Hi' dms and then I block.

@atomicpoet Do people expect a reply when they do that?

I figure they must have pressed return too early and I'll get the first sentence of the message-proper shortly.

Certainly ignoring all messages that are all greet and no meat.