We were able to add tags in a post using a special syntax, like this
[tag:example].
For older posts, they don't appear as tags anymore. Instead they are rendered as hypertext links. This bug is "fixed" if the post is edited and saved again.
This is now:
, this is the usual effect: 
This can be seen on:
Arqade meta, on our "Screenshot of the week" event the screenshot's videogame source is specified in each answer.
New responsive Activity page, every bug, feature-request, status-review and status-completed used in the answers is wrongly rendered
[and]with backslash.s-tagon the class attrubute while it does have thepost-tag. manually adding thes-tagin the DOM via the developer console resolves the issue. No idea what the root cause is but it is something on the SE server side. See i.sstatic.net/YABCbyx7.pngclass="post-tag"while the current HTML render producesclass="s-tag post-tag". The current CSS requires both thes-tagandpost-tagclasses. (sigh. ninja'd)s-tagin the first place. Sure, consistency with Stacks naming conventions, but I think this consistency foolish. They've already stepped back from the (quite flawed, very popular) class-only CSS framework concept, instead choosing to write CSS (!!), so why not preserve HTML semantics while they're at it?