Has this only just been added? 
When typing a post and adding a hashtag a list of categories come up, which when clicked on get inserted as a link.
I think it’s great to add short cuts like this, but categories are not hashtags, and most people would expect to see tags (the closest thing to hashtags Discourse has).
I wonder if anyone else thinks it would be a good idea to use a single # for tags, and two for categories? That would be pretty awesome 
I thought it did tags too… (it does)
##OMG YOU ARE RIGHT!!! THIS IS AWESOME!
I was checking it on a site that didn’t have many tags so only categories showed up
You know what would be really cool now? Some way to more easily add links to threads already posted (it’s such a chore having to skip to another thread, copy the url, go back, paste, then go back to get the title, etc).
And even better would be when users post (external) links the title is automatically added (in the editing box, so it can be changed further).
I bet these are already planned, hehe.
Yes, a way to do inline autocomplete for topics would be amazing. Not too far from the current UX we know, but with topic search.
Atlassian Confluence, of which I am no fan, does this pretty well:
This was covered elsewhere; we don’t think topic completion is a good idea because of the unbounded search space. What if you have 500k topics? That’d be … great…
How exactly is that different than having 500k users? 
A site with 500k users will certainly have more than 500k topics. Unless they are all dead accounts.
Sure, but the user search would face the same challenges as the topic search, would it not? The one actual challenge I could see is if you allow topics with the same title; ambiguity in results would be problematic.
Yeah, to put it mildly. Unbounded topic completion is a super mega bad idea.
How about simply pasting a url and it gets converted to MD format link with the title already in place? Much more efficient and still very useful 
Yeah, to put it mildly. Unbounded topic completion is a super mega bad idea.
How about a compromise to search only the last 100 visited topics for suggestions? This will be almost as useful as searching through all unrelated topics because people tend to only remember and reference what they recently looked at.
This solution will scale well. And in case Discourse hadn’t tracked this info already, we would only need minor changes to the database or we could avoid that altogether and use only JS (although this will not sync across multiple different workstations)
Other topics about this title auto-complete business here:
https://meta.discourse.org/t/how-about-mentioning-topic-feature/7350?u=mcwumbly
https://meta.discourse.org/t/mini-onebox-support/5838?u=mcwumbly