Copilot Chat is rendering identifiers like `__init__` as bold because the response is being interpreted as markdown.

- Copilot Chat Extension Version: v0.55.0
- VS Code Version: 1.135
- OS Version: Windows WSL Ubuntu
- Feature (e.g. agent/edit/ask mode): Chat / Ask mode
- Selected model (e.g. GPT 4.1, Claude 3.7 Sonnet): AUTO; GPT-5.4 mini
- Logs: See screen capture [here](https://github.com/user-attachments/assets/3c5fbdff-ced2-4f29-8582-b7bab63c389a)

Steps to Reproduce:

1. Open Copilot Chat.
2. Ask it to explain or mention a Python identifier containing double underscores, such as `__init__`.
3. Observe that the double underscores are rendered as markdown bold formatting instead of literal text.