This is not the first time I noticed this "problem", but on small screen or resized windows, it could be interesting to mask the side panel in chat. Because sometimes you care to have the largest textwidth as possible.
What do you think?
The minimum screen width we support is 1024 pixels. So that's another 100 pixels more for you (plus that weird [Opera?] bar on the left side). In addition, if you weren't using the userscript that puts the message ids next to the messages, that would give you a lot more space for the text, so maybe turn it off if you have screen real estate issues?
Finally, that room description in The Bridge makes me want to rethink the maximum length for room descriptions :)
Long story short: No. The sidebar is there to stay.