Wikipedia:Customisation

Customisation of Wikipedia allows a registered user to tailor the user experience of Wikipedia according to the user's preferences. User customisation affects only the user's own experience of Wikipedia; it does not affect the reading or editing experience of others. Only registered users can customise their experience of Wikipedia, and the customisation is visible only when the user is logged in.

Among many other things, registered users can the customise the appearance of their signature when posting a comment on a discussion (Talk) page. These signature customisations are visible to all users of Wikipedia.