@amin

Default #Plasma panels are like the windows taskbar, except that they do not have to stretch along the entire length of the side of the screen that they're on.

Floating panels is a relatively recent invention by @niccolove to (optionally) make panels more dock-like by "floating" above the edge of the screen. I'm guessing it was created because #LatteDock (the Plasma-native dock solution) became unmaintained.

The default behavior is that whenever a window touches a floating panel, it "de-floats" and becomes a regular panel. The rationale behind this is that having a panel that a window can't actually touch* is weird, so it's better to revert the floating panel to a regular panel as long as something is touching it.

* My understanding is that windows cannot actually touch the edge of a floating panel because its "hit box" (for lack of the knowledge of a more subject-appropriate term) is larger than the visual part of the panel, because it includes all of the stuff that's in the alpha channel, like the shadows cast by the panel.

My personal feeling on the subject is that an "untouchable" floating panel is more aesthetically pleasing than a floating panel that gets "spooked" like Boo in Mario 64 and reverts to a regular panel whenever a window touches it.

As it is now, I go through the very #OCD route of manually preventing all windows from touching the panel so that it doesn't defloat, because I greatly prefer the floating look.

Anyway, the original post was just me wishing there was a way to turn off the automatic de-float. ;)