Right Right, soooo this is an interesting topic for me, as I am the one that has to maintain these forums.
Right now the biggest pain point in keeping these forums as up to date as possible is this page, interestingly enough most of said pain is a direct result of us making this page have a full width layout.
In base discourse, for those that dont know, the topic page looks like this:
We on the other hand have taken that right column, and moved it under each post and made the content full width. The thing is, the way we did this (before my time) is quite hacky and not really well done. That area still has the same width as the right hand column in meta, and the more that happens to a post, it just stacks there on the bottom right. Not even close to an ideal solution.
To understand why this is an issue for keeping our forums up to date, you need to understand how the plugins work. The plugins allow us to replace templates with our own version, it sort of works like overriding the base template. When the base discourse template changes, we have to go through and compare our custom template and the base template, line by line, to make sure we include all the new things that you all are so keen on 
The template for this page is one of the largest and one of the most complex. And the only reason we still need this custom template is to keep the full width layout. Issues where we have missed minor things have included, not rendering the page at all, i18n issues, buttons not working, not being able to bring up the user cards when you click on an avatar, just to name a few. Luckily we get incredible support from the forum staff and these are usually discovered on our staging servers well before the masses get a chance to see them.
From my perspective this page adds substantial time every time I upgrade the forums to the latest and greatest features. It brings down my confidence in our upgrade process. It adds additional time for our forum staff, and us when they find the inevitable bugs. The time we spend dealing with this sort of thing also removes time we can spend on implementing other features and fixes as we only get so much agreed on time per iteration to work on forum stuff. Not to mention all the messed up mobile version pain this inadvertently causes. The easiest and quickest code to maintain is the code that doesn’t exist.
TL;DR The old two column layout:
- Makes my life easier,
- Costs SitePoint less money
- You get upgrades quicker and new features sooner
- Forum staff can worry less about us breaking things as we aren’t touching as many things.
- Easier for your eyes to track and read shorter line lengths (Heaps of case studies and reports done on this)
Sort of funny how one little change can cause so much headache eh. If you have the choice between a full width layout, and us fixing bugs/adding needed features to make the community a better place, is the full width still worth it?
for transparency