Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 970/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 446.14
Broken: version: 2.83.0, branch: master, commit date: 2020-06-03 14:38, hash: rB211b6c29f771
Short description of error
The sphere that is drawn in the 3D viewport after you select a bone with ik limits has visual artifacts. As far as I can tell, this always happens and requires no special reproduction steps besides creating an armature bone with ik limits enabled under the 'Bone Properties' panel.
Out of curiosity, I took a look at the code. The cause appears to be, that the shader, which is used to the draw the lines of the ik limit overlay, is also used for drawing the sphere. The shader (armature_wire_frag.glsl) does antialiasing for lines, which causes artifacts when it is used for not-lines.
Exact steps for others to reproduce the error
Create an armature with at least 2 bones. Then select a bone and enable ik limits on the x and z axis.