Hi Edison!
Unfortunately, this is not one of those commands that you should be playing with. The brand command is there for specific reasons and as you can see makes changes to various aspects of Comware. For example, the CLI change that you discovered and changes to the SNMP MIB to reflect the newly selected brand.
The only suggestion that I can make to you is that you need to open a support case with us so that we can elevate the issue to Engineering to see if there is a workaround that will allow us to set the brand back to HP. I cannot make any promises on a solution at this point. This will need to be investigated.
Regards,
David