As Lucca says, you have to put Gransnet after your name, or you will just get all references to your user name.
If you do that, you will see a list of your posts, whether or not missing out 'Gransnet' links to other people or things. Try 'Chestnut Gransnet', or 'Buffybee Gransnet' and scroll down a bit.
It really only matters if you have posted identifying information, or if someone like the police has the authority to ask for your IP address (the string of digits that identifies your computer at the time of the post) and can link you directly to your posts.
That is highly unlikely to be a priority for the authorities though, unless you are posting about matters of national security on an open forum without protecting your computer .