The text editor doesn't allow formatting

You are using a browser extension that breaks text editor.

Maybe AdBlock? It seems AdBlock causes the editor panel to be duplicated. In this case, you should see a scrollbar on the right. Scroll down on the editor panel and there may be another editor that actually works.

If it's not AdBlock, try to disable all your extensions to see if any one of those causes the issue. If yes, try to re-enable them one-by-one to figure out which one is the cause.