We could provide that, but since everybody can just create new trade identities whenever he wants, it would be pointless, I guess. Whoever tries to scam people probably does not reuse his trade identity anyway, I would guess.

I put "blocking users" on the list for discussion small features.

Okay, we are on it.
Might still take a week or two, though.

Quick question:
When I scan a private key with mycelium, how does the app treats that key ?   It obviously keeps the key (temporarily or not) waiting for me to act, but what happens to that 'data' after I scanned the key ?

If you scan for import, the key gets stored in mycelium SQLite database in protected memory. If you scan it with the cold spending feature (or the camera button) it's just in protected RAM and will get removed from memory after you made a transaction or hit back button.

It's only kept in RAM for that single transaction.
I am one of the developers of the app, don't know if that is professional enough for you ☺

^^  That

First make sure to create a new backup!
If you are not a beta tester, just send the funds over to another wallet (like on another device, a trezor,  a paper wallet, a wallet with some other service you use anyway etc). Make sure you have backed up all the accounts (if you have non-HD accounts, they are not covered by the word list!). The delete the app data (or uninstall and reinstall) and upon startup, you can create a new master seed. Then send funds back to mycelium.

If you have the beta release available, you can cold-spend from master seeds.
This would allow you skip the step where you send the funds away.
(Make sure to have the backup nonetheless!)
Just delete app data, create new seed, then use the scan button to scan a qr code with the 12 words (for example generated using qrencode - you might want to switch off internet connections on the computer while doing this) and you will be able to use cold-spending from that seed to empty the accounts one after another to your new account. We plan to implement cold spending from typing the word list as well, so you dont need a qr code, but we did not get around do that yet.

I think that would create more problems then it creates.

Even with how it is currently, I ran into this a couple of days ago.

Guy asked me to send a few bitcoins to an address.  I did.   Contacts me that they are not in the wallet and can't spend them, but was able to confirm they are in the address he specified and so all is good.
His mycelium account doesn't show it and the address he had me pay doesn't show either.   This is what was figured out....

He installed mycelium.  Then, made a backup.   Decided to test by uninstalling and reinstalling.   seed worked.  He then cleared the cash files and created a new wallet.   I paid him.
He wanted the wallet on a new tablet and installed mycelium on it and imported the seed.  No coins.   He then went to the first device and uninstalled, reinstalled again using the backup seed. 

Now, both the phone and the tablet have the seed which he made a backup of, but the coins were in the new wallet he had made in order to test out.  Not realizing it wasn't part of the original and backup he made.

$700 gone.

No matter how simple you make something, people will screw it up.

Even if it's not available for download, you would still have it installed.
Also, you could always move the coins to another wallet of your choice if that time comes from an already installed copy.

Remember, you still also have the master seed backup, so you can export all the keys and import to other wallets as well.