This script adds a Winterbash hat-count to every user signature on questions and answers. For example:

Reference this feature request: Show hat count in user card (next to badges).

This userscript requires an engine that supports both @require and GM_xmlhttpRequest. It was tested on Firefox + Greasemonkey and Chrome + Tampermonkey.

To install, click here (Hatoverflow.user.js install at Github).

To preview the source, click here (Hatoverflow.user.js preview at Github).

Notes and known issues:

• No attempt is made to distinguish between users with no hats and users not participating in Winterbash.
• Results are cached for up to 2 hours. This is to avoid hammering the API and tempting the API developers to hammer back. A two-hour update rate is more than fast enough for hat coveting. ;)
• Uses the undocumented Winterbash API, so it's subject to change without notice.
• In some cases, the badge display might get clipped on the right side. This is "won't fix", for now.