Tomasz - the Feedback Center seems to have been down for a little while.
Underlying software that run Feedback Center is retired because it is uses obsolete, unsupported version of PHP and wasn't been updated by source code authors for years.
For security reasons we had to upgrade PHP to most secure and recent version and the FC software is not compatible with it.
Fine - just suggest you put up a gravestone page - and where would you like bugs and suggestions reported ?
Bugs should be reported to SUPPORT email.
As for suggestions - since I have backlog of thousands of suggestions on to-do list I am not really taking new ones, unless you have something extraordinary, then again please write to support email.
FWIW: before setting up "gravestone page" I will be checking if that is possible to somehow fix the old php code quickly.