Do electrum fully support Hierarchical Deterministic Wallets?
BIP32 support is planned for Electrum version 2.0. The code is already there, but disabled.

You can find some features that were first planned for 2.0, but were included in a 1.9.8 release as the servers were being updated to a new important version so it was needed to apply some changes already to the client to put all in place for 2.0 https://bitcointalk.org/index.php?topic=518133.0