You don't need a GUARD at less than 30". I don't know if this in any way is what you might be remembering.

I have never heard of what you're referring to. Maybe someone else has.

The only reference I'm aware of is that you may avoid a handrail if the tread depth matches or exceeds the width of the tread. I am unaware of any other allowances base upon riser height (although a 6 inch ramp, like a curb ramp, does not require a rail either).

1003.5 Exception 2. 

You still have to have one rail. 

For Residential:

Applicable Code: 2012 IRC Section 311.7.8

When Required: Handrails shall be provided on at least one side of each continuous run of treads or flight with four or more risers

Height: 34”–38”

RAMPS 6 inches or less don't need handrails. Under IBC 2015 the floor surface has to contrast with the adjacent areas.

It's for an assembly space. I have an L shaped stair with decorative cheek walls. I'd like to be able to have 1 handrail at the corner of the L instead of at the sides of the cheek walls. Currently 5 risers at 7" with 1'6 tread depth. 

There are some exceptions for means of egress in assembly areas.

1028.

http://publicecodes.cyberregs.com/icod/ibc/2009/icod_ibc_2009_10_sec028.htm

http://publicecodes.cyberregs.com/icod/ibc/2012/icod_ibc_2012_10_sec028.htm