No not a bug. Silent mode is doing exactly what it should it's being quiet.
If you turn off notifications for forum posts on avast.com, you can still go to this forum and read all the posts.
Silent Mode should work similarly. It is supposed to prevent the user from being bothered by Avast while using their PC for other tasks, but if they have double clicked the Avast icon then clearly they want to interact with the program and perform all meaningful tasks. Continuing to hide parts of the program like this is an extremely counter-intuitive design, so I assume it must be a bug, because no competent developer would intentionally do this.
Absolutely not, as different as chalk and cheese. The forum software is from SMF and nothing to do with Avast.
You give Avast an instruction to be Silent and it, no interruptions/silent. When you choose to activate it, there is a little 'i' (information icon) that tells you what you get when using this.
This when it was first introduced many years ago it was called Silent/Gaming mode (no doubt requested by gamers), now it is just named Silent Mode.