filter bone from constraint-selection-Menu

It is actually possible to Bone-Constraint a Bone to itself ('Self-Target').

It's more like a mini-hack in the UI: it requires to use the Copy Constraints to Selected Bones Operation. If we start with 2 Bones (Bone-A and Bone-B), create a Bone Constraint on Bone-B that Targets Bone-A; then, use the said Operator to Copy the Bone Constraint from Bone-B to Bone-A; finally, one can just Delete Bone-B for clean up. The resulting effect, is that the Target was left exactly as it was Copied, even though it was not meant to be possible (?), and an attempt to change the Target option from this point will critically destroy the 'Self-Target' state.

Theoretically, this feature could be useful in the case of a Transformation Bone Constraint for example. Because one of the Bone's Transform (like X-Axis Rotation), can proportially affect another of its Transforms (like Z-Axis Location).

In this whole sense, I'd suggest not to intervene in the UI, if that means risking of reducing Rigging possibilities. I believe maybe the option of 'Self-Target' for Bone Constraint, should be possible in an easier way: maybe a WARNING MESSAGE should appear, but still allow to make it without the mini-hack requirement that I've presented.

If you change the proposition after reconsideration, I can change my Vote to positive. Let's say the UI in this domain is currently inconsistent, but the proposition in itself might be inconsistent as well because it doesn't go deeply enough in the whole problematics, of what should be possible or not, and why something remains possible even though it is obscure (I believe same result could also be obtained by Scripting?). I have an intuition that, although dangerous, 'Self-Target' could be an interesting feature of Bone Constraint Rigging.