I read my IMAP-mail on different computers/mail clients. I wanted to unsubscribe from the majority of my folders in Outlook. Later, I noticed that on another computer, where I use Thunderbird, I was also unsubscribed from those folders as well. This is not what I wanted (at all), so I subscribed again under Thunderbird. The effect was that I also got subscribed again under Outlook.
So I guess this means (un)subscribing to IMAP folders is an account-coupled thing, not a per-client thing. Is there a way to achieve (un)subscribing per client?