The forum CSS is an absolute mess, presumably dynamically served (I'm not a web developer). There's a min-width parameter that forces the ridiculous width.

This isn't a perfect fix but overriding it with:

body {min-width: 450px;}

... at least fits the text on the screen. There are several extensions that will allow custom CSS for each desktop browser. Firefox on phones may support this.

If anyone wants to add some suggestions for keeping the lines to about 10 words & centering the column/DIV that the posts reside in, please do.