Replying to a group message from different address changes the member list - bug or feature?

If you can, use the deltachat core for your project. https://github.com/deltachat/deltachat-core-rust
It’s written in rust and has also a C-api for which you could create bindings for Go.
https://c.delta.chat/ - documentation for the deltachat-ffi (c api)
When using the deltachat core you don’t need to interact with email or encryption directly, the core exposes a “high level” api that gives you access to chats, contacts, messages and so on.

We have an Impersonate feature planned: BOT - Impersonate / Alias names.

Here are 3 bots made with deltachat core for reference purposes: