I mostly read rather than write in my own TiddlyWiki. That also goes for the web at large. So I am used to autoscrolling - which is especially useful when I have many tiddlers open - and I do most of the time. I don’t have any wrist problems and rarely copy texts. So it really depends on how you use it.
You
By default, TiddlyWiki doesn’t know what tiddler you are focused on. There are a number of plugins that offer this functionality, though.
I found TiddlyFlex executes this very well, if you are open to its style of layout.