If three HA nodes are configured as follows:
> /vsmserver/HA/nodes=foo bar baz
The master will log the following in /var/log/vsmserver.log:
> ERROR vsmserver.HA: /vsmserver/HA/nodes contains more than two entries, which is not a supported configuration
After this, the master will start up as normal, but with HA disabled. If this log line is missed by the system administrator, they may think HA is enabled when in fact it is not.
Looking at the HA chapter in the TAG, it is not obvious that HA setups with more than two nodes are not supported. The text describing how you set up two-node HA may be read as one example of how HA can be configured, and not as the only possible way we allow HA to be configured.