On testnet, a dumpwallet/importwallet cycle loses all labels and seems to mismanage addresses.
- Receive some coins
 - Name the receving address in the transaction list GUI by clicking “Edit label”
 - dumpwallet
 - Make new wallet
 - importwallet
 
Notice, that the label is lost. Also, the “File->Receiving addresses” list shows a wrong address starting with m....
This does work on mainnet.
Also, importwallet does not trigger a rescan on testnet but does on mainnet.
This is v0.16.0.