ServerConfigurationService implementation has been improved to support both styles of defining sakai.property lists (CSV and numbered lists). This is true for at least 12 and 19, possibly even earlier.

It's been 7 years, so my memory may be a bit rusty, but here's how I think the sakai.properties should be configured:

Note that "msgcntr.rolesnone.count=#" needs to be there and be accurate for the # of roles listed.  I'm a bit surprised that a comma delimited list worked, but I'm not enough of an expert in the sakai.properties parsing to know how it works.

Thank you so much, all.

The below two properties did not affect the behavior:

msgcntr.groupsnone.1 = access
msgcntr.groupsnone.2 = Student

However, msgcntr.rolesnone=Student,access did the trick. It works as I wanted and expected.

Thank you again

The msgcntr.rolesnone configuration option is only used when topics are created using "Automatically create multiple topics for groups" option.  And it's only when it creates the groups.  So if you're only creating one topic, it has no effect whatsoever. 

On the other hand, if the settings are configured (typically for "Student" and "Guest" roles) then when you use the "Automatically create multiple topics for groups" the topics are preconfigured to enable "Contributor" for the groups and "None" for the roles specified by msgcntr.rolesnone. 

TL;DR: If the msgcntr.rolesnone settings are configured then the topics that are automatically created only allow students to see the topic for their group. 

Confirmed; it should only affect group topics.