If this is just a display issue, it's still fairly significant because a tolerance of 0 and anything else are very different. I have not confirmed if it's only display or if the comparison is actually using 0 (which would be project-breaking in some cases).
Also of note is that 0.0000001 is truncated to 0 if you type it in.
Place a Vector NotEqual / != node in the BP editor. Observe that the Tolerance value is displayed as 0.0. The actual value in code is 0.0001 (1e-4), which if you were to type it in would fit and not be changed to 0.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-170835 in the post.