D's greatest mistakes

[Nick Sabalausky]

"Steven Schveighoffer" <schveiguy at yahoo.com> wrote in message 
news:op.vmxqi4kmeav7ka at steve-laptop...
> On Sun, 28 Nov 2010 23:19:44 -0500, Jack <jt at overlook.biz> wrote:
>
>> The post "C#'s greatest mistakes" prompts/begs this post. Have at it,
>> pick up the ball and run with it, don't be shy. I expect Walter and
>> Andrei to answer (if Walter and Andrei so dare!) after others' posts have
>> stopped or stagnated into that cesspool of threaded discussion that is
>> "the subthread" or "tangential thread" (which surely needs a rock
>> anthem).
>
> As I understand this is a troll post, but still provoked some good 
> discussion, I'll throw in my biggest problem with D:
>
> lack of tail-const/immutable for classes.
>

I've heard this before, but I'm a little unclear. Can you give an example?