I know this is a necro bump. But... others may see it from google searches. 

Thanks for the answer! I don't really understand how this can be used if I "own" tho whole second level domain, but I will try and google a bit more with that keywords.

Don't think the abuse in question is much about people attacking someone else's domains, but rather people using their own domains with the intent of abuse. For example phishing scams could dynamically respond to hundreds of different possible aliases, with a legit looking domain in the front of the alias.

Sad, that some people abusing this take a usefull feature away from all people

They didn't remove the feature, they just put the feature into the hands of the DNS admins, which you'll need to email  dnsadmin@he.net in order to request it's addition or modification.

I wonder what kind of abuse they speak of? It's rather disappointing though when it comes to dynamic applications to not have wildcard DNS available (and I'd prefer not to go back to using something like namecheap's DNS etc).