It is not safe to use a portable version of Electrum on an insecure computer!
What does it mean "insecure"? In which manner?
I didn't read the whole thread. If I should do this, please let me know.
It is 'insecure' in terms of that it encourages bad habits (using as portable wallet on multiple computers).
The security itself (if used on a secure computer) is the same as with any other wallet (either installed electrum or other wallets).
The security completely depends on the computer it is running on.
I have also replied in your thread regarding armory/electrum.