Although there have been and will always be
discussions on this issue ... it is common practice and
supported by VMware to run your vCenter server in a Virtual Machine. I would even consider this best practice, because then you will have the high availability and all other advantages that a VM has over a physical server.
However, there are some things to keep in mind with such a setup. You might for example run into a situation where you lose access to vCenter, e.g. because of a network or storage issue, a guest OS crash in the vCenter VM or a host failure that is - for some reason - not accommodated for by HA (although HA does work independently from vCenter!). In such a situation you better know
on what host your virtual vCenter runs (or was running), because you need to connect to this host to troubleshoot and resolve the issue and get things up and running again. The same applies to the VM that runs the vCenter database (if this is a separate one).