Yes, I would say it's a feature, bot a bug. There was a brief phase when social networks first came about when everyone was fine just putting their entire life on display. Then everyone realized that privacy is kind of nice. You don't want all your stuff out there long-term easily findable and for everyone to see. You don't need absolute privacy either. You have no problem talking about things with your friends in public, even though strangers might eavesdrop. The same holds on discord. Anyone could listen in on your conversations, but it's unlikely enough that it doesn't really matter.