Here is a copy the private message from the moderator that was sent after my post to the meta.

> Hello,
>
> I'm writing in reference to your Statistical Analysis - Stack Exchange account:
>
> https://stats.stackexchange.com/users/3911/gaborgulya
> 
> It seems you have added a tag "analytical-derivation" to many questions. As you can see, this tag has been wiped out. There are two reasons why we did that:
>
>    * This tag was a meta tag, and as such it was not making Internet a better place; this blog post explains it in detail: http://blog.stackoverflow.com/2010/08/the-death-of-meta-tags/
>    * SE is a collaborative site, and the organic growth of a tag is the only way to ensure that it is wanted and needed.
>
> For the future, if you think that some global editing action is required, propose it earlier as a meta thread.
>
> Regards,
> XXXX
> Statistical Analysis - Stack Exchange moderator

I'm not sure the moderator wants to identify themselves so I substituted the name with XXXX.