I want to remove the discussion/talk tab from my wiki so bots don't find it ruining my domain authority.
Topic on Project:Support desk
There are these few lines of CSS code, which you put on the wiki page MediaWiki:Common.css and they will no longer be displayed. I don't know them out of my head right now; basically I would google that. Is it really that this information is not findable?
That just hides the Discussion page. doesn't remove it from the wiki
So what are you aiming at? Do you want clean HTML source code? Or do you also want MediaWiki to remove all links to discussion pages? Do you want to remove the whole Talk namespace? That surely is all possible - somehow. The question only is: What is it good for? The CSS hides the tab and in so far basically makes the pages invisible. People can still type in the URL manually, but why should they do that, if all they find would be an empty page? The CSS is the way to go.
When you are measuring SEO/Domain Authority it is ruined by having a bunch of empty pages. That is why being able to remove all of the discussion pages would be very helpful
If you are worried about bots/search engines indexing your talk pages, maybe modifying the robots.txt accordingly could be an idea you'd like to follow (see Manual:robots.txt).
That is what I am doing as well. However, for me the reasoning behind disallowing robots to access Talk: pages is not that I would fear that they would not understand the meaning of "error 404", but that I consider the discussions on Talk: pages not to be article content and so I don't want it to show up on Google and such.
What code would I need to add to no index the discussion pages?
E.g. something like this:
User-agent: * Disallow: /Talk
This disallows access to all pages starting with "Talk". If you use a different URL structure, maybe you want to adjust the line so that it fits your structure accordingly. Should you use something like Google Webmaster tools, you can check there to let Google tell you, if your lines work the way you want them to.