You and I both.

Except it's not a bug that found use. It's intentional behavior. From https://specifications.freedesktop.org/clipboard/latest/:

> The rationale for this behavior is mostly that [having a unified clipboard] has a lot of problems, namely:

> - inconsistent with Mac/Windows

> - confusingly, selecting anything overwrites the clipboard

> - not efficient with a tool such as xclipboard [(tool that maintains a history of specifically CLIPBOARD; it would be messy to keep a history of all selections)]

> - you should be able to select text, then paste the clipboard over it, but that doesn’t work if the selection and clipboard are the same

> - the Copy menu item is useless and does nothing, which is confusing

> - if you think of PRIMARY as the current selection, Cut doesn’t make any sense since the selection simultaneously disappears and becomes the current selection

The selection buffer is easier to understand if thought about more simply. Middle click to “put my selection here”.

The actual clipboard is a separate feature in my mind.

Yup, both have their uses. If you use a clipboard manager or have the clipboard synchronized between devices/remote desktops/VMs, the primary selection comes in handy for stuff you don't exactly want saved to disk, crossing VM boundaries, or transmitted over the network. I use middle-click pasting primarily for its separate buffer.