I'm certainly not angry about making a suggestion, I don't want to discourage ideas in general, but you are right if you guessed I would not like this idea.
These pages are not CMS pages and they have no page id associated with them, so what you are really requesting is to show the side column content of the default page (ie the home page) (if it happens to have any side column content) on all of these pages. I am not keen on this idea.
There is already a way to do it if you have some side content that you want to show on all pages including the pages you mention. As you know you can put anything in layout.master and it will show on all pages, but if you want to be able to edit that content then you could use ModuleWrapper in layout.master to load a specific instance of Html content. If you put it in a side column (ie divLeft or divRight) in layout.master you can force it to always use the column layout to show that content.
To be honest I'm not a fan of the ModuleWrapper either but it does already exist and it does make it possible and quite a few people do already use it for this kind of thing.
Some of these pages are secure pages, Login, Register, UserProfile, etc, particularly on the Login and Register pages I think it is not a good idea to distract the user with content. But also once a user can edit content there then they can make some mistake like linking to an img src="http://... and then since it is not using https it will give the user a browser warning about insecure and secure content on these secure (https) pages.
Requests like this are a slippery slope, it would be easy enough to implement this and add config settings for what you requested but then next someone will want it to be site specific and then someone will want to be able to have different editable content on each of those pages. All steps down a road where I would rather not go and each step makes it easier for the next guy to ask for the next step. To me there are good reasons why most of those pages should not have extra unrelated content on them.
So hopefully the ModuleWrapper solution will meet your needs.