I’m not sure why, but the vertical writing mode css line seems to control both the tight padding around the text (which you do want) and the distributed spacing across the screen (which you don’t want). In my inspector, deselecting that writing-mode line solved the one problem at the expense of the other.
I don’t understand how to reproduce what you show in the image, in the actual wiki you link to. It would be better if you linked to a wiki that directly shows the problem.
There is filter button in the topbar to the left of the select widget. Click that button to change the tiddler count to a small number like 5…That would be sufficient to reproduce the problem…