Custom posting formats (eg pulsing, direct, etc) are not supported by Lucene - they provide no bwc promise. We removed the documentation before 1.4.0.Beta1, and we should prevent users from using these codecs going forward.

At the very least, we should deprecate custom codecs and refuse to create new indices that use them. I don't know how widely used these are (I'd imagine not very widely at all), but I'd be tempted to remove them completely in 2.0.