Is it possible any form of font size customization in Community Edition of XWiki? If not possible for the user for an installed application, I guess I could play with certain files at the prebuilt stage. Any suggestions in this regard are greatly appreciated.
There’s only one version of XWiki: XWiki Standard 
(no community edition).
You can customize the font size for the wiki by checking the Color Theme used (you can change the font there). If you want a different font or size for a given user, I guess this currently has to be done at the browser level.