I contacted Customer Support to get my digital SE but it seems they reply me with some automated answers which are useless

I managed to get a copy of CE and upgraded about 2 weeks ago from my Standard Edition copy. I can confirm that you can transfer your old SE copy to someone else.

Point to note though, DO NOT send your ticket though SEA. I waited over a week for a reply with no luck. Switch your location to the Americas (Lower right of the website and select Americas - ENG (US).

I put the ticket up under the section: " I want to make a suggestion or a complaint"

Then include the following details:
SE and CE CD-KEY
Your account name

Friend's account detail (or whoever you plan to transfer the SE key to)
First name
Last name
Email
Address
Battletag

Within 2 days I got a standard cut and paste reply which was of no help, but a quick reply/update of the ticket and another CSR was able to transfer the SE Key to my friend's account within 12 hours 

Good luck! 

We can get a normal cdkey priced @180 , u srs?