Re: Is there a way for me to use a Mycelium HD wallet in Electrum or vise versa?
Were the addresses shown in Mycelium HD the same ones as were shown in Electrum? I thought they would be different because one wallet uses compressed keys and the other uses uncompressed keys.
This is what I wanted to know as well... as others have indicated that even though you can get Electrum to accept the Seed words from Mycelium, because of the whole compressed/uncompressed keys thing... The result being that Electrum ends up "generating" different keys/addresses from the same seed? 
However, I decided to just give it a go... downloaded Electrum onto the PC and used my Mycelium seed words (along with BIP39 seed option)...
The result: It has (re)created my wallet succesfully... all address (used and unused) match up... and it has even retrieved all the transactions!
Thanks for testing it out for yourself. After some googling I found out that electrum switched from using uncompressed keys to using compressed keys.
electum 1.9 (the upcoming release) will use BIP32, and therefore compressed keys
Looking at the release notes it must have been after electum 1.9.
https://github.com/spesmilo/electrum/blob/master/RELEASE-NOTES
I tested exporting a private key from electrum 2.7.17, and it began with k (which means WIF-compressed). However, when I tested exporting a private key from electrum 1.9 it began with 5 (which means uncompressed WIF).
http://chimera.labs.oreilly.com/books/1234000001802/ch04.html#_key_formats
Quote
In a newer wallet that implements compressed public keys, the private keys will only ever be exported as WIF-compressed (with a K or L prefix). If the wallet is an older implementation and does not use compressed public keys, the private keys will only ever be exported as WIF (with a 5 prefix).
I decided to test it out for myself, but I could only generate one address in mycelium. I think I have to send Bitcoins to it before it will generate another.
Importing the mycelium wallet's words into electrum generated that first address OK.
When I tested using a multibit HD seed in electrum it didn't work. Although I assumed that was due to compressed/uncompressed keys it must be due to some other problem. Ranochigo says it's because the two wallets use different seed derivation methods.
AFAIK, you can't import anything into Multibit HD and they don't adopt the same seed deviation method as Electrum.