Hey, can I create signature so that it will appear below all my posts and comments?

Yeah, we also support signatures. You can create your signature by clicking on "My account" on top black navigation bar, click on "Edit" tab, and scroll down to "Signature settings" section (above "Picture" section).

Enter your signature there (a verse from bible or a quote from saint would be cool!) and click on "Save" button below the page. That should do :).