Inconsistent interaction still remains for inserters that are dropping onto a splitter from behind the splitter (regardless of splitter orientation). They still drop on the output side, leaving the items unavailable to the other side of the splitter. Here is a test of all orientations on 0.12.31, showing that most of the issues have been resolved except for the case of the inserter being behind the splitter:
For reference, here is the same test on 0.12.29 (and presumably 0.12.30 although I did not verify):
Blueprint string for the test layout:
Blueprint
I've filed this as a new bug report since the previous one was marked as fixed (and it mostly was).