This issue occurs for Linux 64-bit and Windows 7 64-bit. 32-Bit untested.
Currently, the local chat window has no limit on the amount of text it holds and displays to the user. The user can read every bit of chat since his or her log-in.
The problem with this is, after a heavy amount of chat has been recorded over time, the local chat window begins to freeze the entire viewer when new lines of chat are added. The effects get gradually worse to the point that the viewer locks up for seconds at a time everytime a person nearby enters a new line of chat. This can potentially crash the viewer if the user does not relog or clear his or her chat.
I think the local chat window needs a limit to the amount of text it can hold before clearing the oldest lines of chat to make room for new lines. But by all means, any better solution is good too.
Lubuntu 14.04.3 LTS 64-Bit
CPU: Intel(R) Core(TM) i5 CPU 650 @ 3.20GHz (3201 MHz)
Memory: 7912 MB
OS Version: Linux 3.13.0-63-generic #103-Ubuntu SMP Fri Aug 14 21:42:59 UTC 2015 x86_64
Graphics Card Vendor: NVIDIA Corporation
Graphics Card: GeForce GTX 660/PCIe/SSE2
OpenGL Version: 4.4.0 NVIDIA 340.76
RLV Version: RLV v2.8.0 / RLVa v1.4.10a
Windows 7 64-Bit