Thanks for filing this.

I should note that what would be most functional is a system that lets me post a link (meaning a wikilink or a URL) that represents the command. I want anyone to be able to do this, not just the devs. Something like:

"Click [[Special:ChangePreferences/scary-code-name-for-pref |here]] to toggle the tickbox for that pref"

(or whatever format is necessary) would be great.

I don't understand this bug. We have plenty of one-click preference change systems, which alter the preferences via WebAPI. As one prominent example, see [[mw:ULS]].
I recommend filing a separate bug for each preference you want one such control for, specifying if it can also supplant the Special:Preferences checkbox (cf. bug 32811; keep bug 31882 in mind).

Unless requirements for this request to be considered fulfilled are clarified, I propose RESOLVED WORKSFORME.

(In reply to Nemo from comment #2)

I don't understand this bug. We have plenty of one-click preference change
systems, which alter the preferences via WebAPI. As one prominent example,
see [[mw:ULS]].

I think you have mis-understood this request; it's asking for a consistent, MW-provided system to do this that works the same way for all preferences, and which each feature can trivially provide, not specific ad-hoc hacks like ULS etc. use which mean users have to learn them each time.

(In reply to James Forrester from comment #3)

I think you have mis-understood this request; it's asking for a consistent,
MW-provided system to do this that works the same way for all preferences

The WebAPI works for all preferences. Can you clarify the requirements, as you're so sure about them?

I think I can:

Tell me the exact wikitext I need to type to tell an editor at the English Wikipedia's Help Desk these things:

"Click HERE to disable MediaViewer"

"Click HERE to opt into the Beta Feature VisualEditor"

"Click HERE to set your default image size to 300 px"

"Click HERE to set your gender to female"

"Click HERE to turn on Twinkle"

"Click HERE to turn off Navpops"

"Click HERE to set your default image size to 300 px"

"Click HERE to set your gender to female"

(In reply to WhatamIdoing from comment #5)

I think I can:

Tell me the exact wikitext I need to type to tell an editor at the English
Wikipedia's Help Desk these things:

"Click HERE to disable MediaViewer"

Don't write "click here".

http://www.w3.org/QA/Tips/noClickHere

[…]

"Click HERE to set your gender to female"

whatever ajax appears should be clear on privacy implications (value is published) and what exactly it's used for. (software strings not stats, etc) also, remember a11y, aria, etc.

As GET requests (navigating to a URL) now have to be read-only, this feature would at best be two clicks. The link would need to take you to a page that had a confirm button that triggered the POST request to update your preference.

The only way to make this one click would be to use JavaScript, but then you aren't talking about a simple wiki link.