Remember you are not working alone. Different people/companies work differently, but nearly every job has - at least once in a while - a time when someone will be ask your computer reading something on your screen with you. vi vs emacs is bad enough, but at least I know how to do minimal navigation, save, and exit from each (I expect that advanced users of those tools can do much more): there are only so many different systems I can learn though, and it is unfair to make everyone have to learn another. Thus emacs should not allow your to customize your environment with local scripts, either it is in base (as IT installed it), or it isn't allowed! (to my knowledge vi/vim doesn't allow this). Similar for other tools, if it isn't easy for someone who isn't an expert: either your company shouldn't allow it at all, or they need to ensure everyone is encouraged to get training (not forced in case you wouldn't do that anyway - but it should be automatic if you want it and you should know you can get it)

Font size - I've worked with nearly blind people who need huge fonts just to see/read. However this is a compromise and they are worse developers for lack of ability to see as much text as a smaller font enables. Don't get me wrong, they are still great developers, but their eyes are a limit to how good they can be. It is thus reasonable to have a configurable accommodation for that. There are a number of other examples where things can be configurable, but the configurations should be controlled and easy to find. (I'm color blind, if you allow color coding that is fine so long as I can find a color that works for me)