The zebra-table demos are using an ability (to affect content on the page outside of the template's output) that is specifically warned against in Extension:TemplateStyles#Caveats.
Personally I don't care much for that restriction, but some others really want it. Perhaps the demo should be changed to avoid doing that.
Irony fixed. Something like that is needed for crazy pages such as this:
It had around 7000 template calls just to add a different color to some links, it also had more than 10000 unnecessary html span tags just to also change color of certain links.
While that's a horrible case caused by user ignorance, it still highlights the fact that currently adding repetitive styles to pages is a inefficient. Bloating common.css with these would also not solve the problem in a huge wiki such as german wikipedia, nor would changing those 7000 templates to call TemplateStyles internally.
That particular case was changed, but the underlying problem remains. Although it could be argued that it isn't a problem meant to be solved by this extension.
Perhaps that could work in a future "page styles" tool, or something similar.
If there is one thing mediawiki developers probably realized by now it is that any mechanism added to a wiki will be abused (templates -> slow pages, gadgets -> broken pages and features) . If this ironic usage is an anti-pattern, it might be a good idea to start thinking about ways to minimise its impact or abuse.
Experience tells us that the best way to avoid such abuse is to break things hard and fast whenever they happen.
