User blog comment:BertH/Fluid layout has arrived/@comment-3467474-20131205162727/@comment-452-20131205170649

Changing the font to 13pt site-wide without permission violates the TOU.
 * edit: No, it won't. See BertH's comment here

If Wikia Staff give you permission to do something which would otherwise violate the TOU, it's not a TOU violation.

If you have a good reason to need the font-size to be 13px, tell Wikia Staff via Special:Contact, and link them to specific examples of pages which need to be 13px, and maybe they'll see things your way.