For all the janky looking URLs I get from eggs that only have like twenty tweets, half of them janky looking URLs, I don't believe anything is trivial for Twitter's spam filters.

Maybe? They never did anything with the proof of concept ones I worked up, but I never did anything with them other than basic interactions with the network.

I'd guess there are enough duplicate tweets. "Another crappy day at work", "looking forward to dinner tonight", "going to see my sister this weekend!", etc. That I doubt it'd be a very useful heuristic.