we do not share your data with anyone and there are many ways to control the visibility and storage life of your data here.
but the internet is a public space and you should always assume your data could be compromised.
be smart with your password, use tor or a vpn, and use pgp for sensitive communications.
If you are not seen your item on items page.
Either your too new or just not interacting with ppl through posts comments etc. Get to know your market an the market will do the rest.