Some thoughts:
I remember I would write whole ass essays in the tag section of tumblr. In a way, the tag section conveyed a loud quiet voice—the hashtag had symbolized a liminal space between a fully developed thought and silent indifference.
- Tags represented a more stream of consciousness style method of communication without the typical rule sets of language and punctuation
- An entirely different thought is its own tag
- A drawn out laughter could be a tag
- Great ideas could be a tag
- Some tags were utilitarian, others would be purely reactionary
And most importantly, tags were your own and on your blog only. They could not be transferred every time someone reblogs (unless someone screenshotted them and used it as an image). So unlike captions which could be shared and embedded into the post, tags were an exclusive way to communicate to your community and the people interacting with your blog directly.