Topband: Feedline Grounding and Feedline Chokes

[Bob K6ZZ]

Folks,

I see a lot of references to grounding coaxial feedlines at the top of
towers, bottom of towers, and at house entry points.  Is this purely for
static and lightening protection purposes or does it also help mitigate
Common Mode problems as well?

If feedlines are well grounded, are chokes still useful for controlling
Common Modes problems?  I suspect that both can be used, and should be
used, in a well designed station.

Are there specific recommendations on the use of chokes on grounded
feedlines?  Does placement matter?

Thanks, Bob K6ZZ