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This seems more likely as hashtags and mentions both came from how users were using Twitter, they weren't originally in Twitter.

That's just spin. Facebook has picked the right bandwagon so Twitter is jumping on. At the end of the day, it's just a link on a website.

I would be more sympathetic to that explanation if the feature being rolled out was somehow novel or at least adding new functionality. But it's not, it's just removing a small quirk and making the service more like everything else on the internet.