Something is still wrong--this doesn't make sense. It looks like the solution is to remove all of theseabs calls, and instead setx = abs(x) right after saving the sign of x, a few lines above.

Also, if the LogFormatter is going to handle negative values, this should be explained in the docstring.

The LogFormatter is used with the SymmetricalLogLocator so it should (and probably always has) deal with negative value. But the LogLocator doesn't deal with negative values.

I'll fix the abs stuff. Another solution is not to deal with the sign as it is done in the other formatter (or remove the explicit dealing with sign as it is done right now, I am not sure why)
Honestly, I think this whole part should be refactored and rewritten. I just wanted a quick and easy fix in this PR, as this is a critical bug for 2.0 and don't think we should refactor all this before the release.

I think that dealing with the sign separately is a simplification; all the logic can work with conditions based onx>0, as appropriate for logs. The generalization to make it usable for symlog is then just a matter of stripping off the sign at the start and putting it back at the end.