You can now use the equivalent of hashtags, which I just call tags. You'll notice a Tag button when composing messages. Just use that on some text, and it'll insert code that makes it work like a hashtag. Don't remove the underscores, or it won't work.
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This is pretty exciting for me, especially as you can add lots of tags at once, and the feature shouldn't slow the site down.
I consider the idea of how to do it miraculous.