Thank you for the work, @baris
Edit: Can confirm that this is fixed. The topic can be closed (if needed)
@marcos2 The tag box only appears when creating a new topic. So the space you're losing is down to that. When you're replying to an already existing topic, you don't have that tag box taking up the extra pixels.
Increasing the composer size is a solution for now, but I guess that's the issue when using a small laptop. (13inch Mac?)