Most instances don't have a specific copyright in their ToS, which is basically how copyright is handled on corporate social media (Meta/X/Reddit owns license rights to whatever you post on their platform when you click "Agree"). I've noticed some people including Copyright notices in posts (mostly to prevent AI use). Is this necessary, or is the creator the automatic copyright owner? Does adding the copyright/license information do anything?
Please note if you have legal credentials in your reply. (I'm in the USA, but I'd be interested to hear about other jurisdictions if there are differences)
In the vast majority of countries, everything written down is automatically copyrighted by default and if you want to release it into the public domain or under a free license you have to make it explicit.
It’s not really fully determined whether you can actually release something to the public domain, since the “public domain” is not a legally sanctioned entity. It’s just the name we use for things that are uncopyrightable or otherwise not copyrighted (like certain government works, or works old enough that the copyrights have expired). The CC0 license from Creative Commons gets around this by waiving all copyrights instead.
This waiver nullifies and voids all copyright on a work. It also provides a fallback all-permissive license in case the waiver is deemed legally invalid. In the worst case that even the license is deemed invalid, the license contains a promise from the copyright holder not to exercise any copyrights he/she owns in the work.
I'm writing this response mainly for the purpose of bringing it to the public domain. Feel free to screenshot, copy, and distribute however you see fit.