Show or Hide the Page Tabs
Steps
Comments, Annotations, Attachments, History and Information are tabs of a page in the page extra area. To turn each of them on or off, for the whole wiki or for one Page:
- Administer the wiki.
- Open "Look & Feel" > "Presentation".

- Set each of the five fields to "Yes" or "No":

- Click "Save".
- Open any Page: the strip now holds only the tabs you left on, and the first of them opens by itself.

The same five fields are on a single Page's own administration: administer the Page and open its "Presentation" section. A Page takes the setting from its own administration first, then from the Pages above it, and only then from the wiki, so turning Comments off on a parent turns them off for everything nested under it.
FAQ
Why is there no Annotations tab?
Because the standard flavor ships "Show page annotations" set to "No", so a stock wiki has four tabs rather than five. Setting it to "Yes" is not always enough on its own: the Annotations application also has to be activated, and the Page must not be among the ones excluded from it, both under "Content" > "Annotations".
Why is the tab still there when I set the value by hand?
Only the exact values 0, no and false hide a tab. Any other value shows it, including off, No with a capital and an empty value. An unset field is why the other tabs appear without anyone turning them on. The administration's "No" stores 0, so the screens above never run into this; editing the object or the configuration file by hand can.
Can the tabs depend on who is looking?
Not from the administration, which only knows Yes and No. For a rule, override layoutExtraVars.vm in your own skin:
#if (!$hasAdmin)
## Hide the tabs
#set ($displayDocExtra = false)
## Hide the viewer shortcuts in the menu
#set ($displayShortcuts = false)
#end$displayDocExtra hides the whole tab strip at once, whatever the five fields say. $displayShortcuts is a different thing: it hides the shortcut entries of the content menu, which are not tabs.
Put the override in your own skin, not in the copy of layoutExtraVars.vm inside the web application: the shipped file is deliberately empty for skins to override, and upgrading XWiki replaces it.