When posting original content, like media, code or pieces of writing one of the concerns people may have is over copyright. If it is a concern, then it is best reading up on how you can protect your work before posting. Do not think of what you post on this website as proof that it's originally your content, my recommendation would be to link people to somewhere that is a little more secure.
I used to use a website that'd convert your writing into a PDF and place a signature on it to date it for you so that you are able to prove the date you created it, sadly the website no longer exists and I don't know of any alternatives or any solutions for other forms of media. If any members have any recommendations they're welcome to post them.
Whatever you post is your responsibility.