Currently DDMD relies on doing this, so turning it into an error will have to wait.
Comment #2 by ibuclaw — 2015-04-26T10:06:13Z
It's been in deprecation since 2.004 (I didn't realise it was /that/ long ago).
Updating deprecated documentation as a start to reflect this: https://github.com/D-Programming-Language/dlang.org/pull/980
@yebblies, I'm happy with delaying removal until post DDMD switch-over.