It does allow you to watch a question. Check your profile for more.
You will see a favorites tab on your profile. Clicking on it will show the list of questions you either want to come back to or track in some way.
When you click that star it does allow you to track the activity on it.
You may notice after a while, when logged in, the tab may have a ...
Use any CSS customization browser extension and change the style of .tagged-interesting, e.g.
background-color: red !important;
Make sure you declare your changes !important so they don't get overridden by the site style.
To customize the presentation of ignored tags, change the style of .tagged-ignored.
You can do this (even across sites) on http://stackexchange.com.
Open your profile, go to Filtered Questions, specify the rules (tags and sites), and save.
Open the newly created filter, and scroll to the bottom.