What are you reporting as a bug?
The fact that the scrollbar thumb got larger after you scrolled up?
I might say this is a result of chat buffer space being deleted and the scrollbar thumb is only updated when you use it.
If you want to increase your chat buffer size, goto File > Options > General > "Window Buffer" and increase its value to 1024 to 4196 lines. You can go higher, but be prepared for significant memory and resource usage.
- Raccoon
