Posted on: 01/26/21 06:42PM
That's not really how cookies work, and it also isn't how the old layout worked.
The layout change isn't just a change to the CSS. What actually gets sent from the server has changed in ways that are incompatible with the old layout. If we tried to load in the old layout on top of the new layout, a lot of important elements just would not show up due to fundamental differences in the way they display. Making them display would require a significant amount of JavaScript to interpret the page to place, for example, the unread mail message, or the pool message, or a way to view the fullsize version of an image on the page. This would also require us to support and develop for two views each in two entirely different layouts going forward, and this is something we definitely cannot do. If you want to create a UserScript and wrapper to do this for yourself, please feel free.
Keeping a toggle in user settings would avoid needing the JavaScript, but once again, we do not have a view component that can be neatly separated from the rest of the code and swapped out. Serving out the old layout on the server side would mean serving an entirely different PHP file to people with that setting. This means that all of that code would be duplicated, and whenever anything on the site changed at all, even something entirely on the backend that an end user wouldn't even see such as a change to the database schema, we would need to do the same work twice. Again, this is something we definitely won't do.
The solution to that would be to refactor to use a MVC model where we can just swap out the view component, but this would take months to finish, if not more than a year. We needed a mobile compliant layout immediately. We also have some planned backend changes, bug fixes, and feature improvements planned, all of which are important and would have to be put off for that entire time that we were converting the site.
Finally, if the Google crawler somehow sets itself to use the old layout (which I wouldn't be surprised if Google did on purpose to spite us for daring to offer users the choice of a layout that hasn't earned their approval), we would once again fail Google's mobile usability audit, which is the entire reason we made the new layout to begin with.
tl;dr however you slice it, offering and maintaining both layouts is technically infeasible.