Do "Tags" in Wordpress and other blogging platforms increase off-site SEO?

I think tags are used more for on-site SEO.
They help to improve searchablity of a particular article on the blog.

I advice you to choose one tag per article, it's has no impact on on-off site SEO, its more about getting easy to visitor to find this article when he action a search on the blog.

Yes, I think blogging or Tags in blogging sites  builds very White Hat and clean Backlinks.

The link we will add to the article and back to our site is ‘in content’. The links are not rented or paid links, and the sites used are good quality blogs.

 

Blogging sites like Wordpress, bolgspot, weebly, squidoo ETC. helps you get good backlinks and also  this sites helps you post your blogs and gives you a unique URL of your blog with which and you can even bookmark the URL of the blog to increase the visibility of the blogs.