Marker trait and Comma

A Marker is defined with a string including a Comma (,); the string is truncated from the comma onwards.
If the escape character () is used, the comma / string will be defined correctly.

Is this expected behaviour ?

Yes. The comma lets you define multiple markers in the same entry.

From the online help:

Thanks Brian. On this occasion, I didn’t think to look at the help. My mistake.

I admit I don’t see the use of the combined Marker syntax compared with defining the markers with individual Marker traits. I suppose it offers a concise way to define a set of markers. Is that it?

I guess so - I don’t actually remember to use it either, but I imagine that was the idea. Fewer entries in the trait list improves performance marginally.