The question was never, is "West Advisor" an authority, but rather do DIY's read this sort of thing on the net and believe it. There is soooooo much easy to find poor information on this subject it is scary. There are multiple formulas out there so much so that it can be dizzying for a DIY. Everyone seems to have an idea of what is safe, unregulated. I suspect very, very few have ever sat down and done the physical testing to prove their formula in the real world.

One well respected authority, Nigel Calder, says a panel of 0.5% of the 20 hour rate, or approx 1.1A for a 200 Ah bank, is safe. Yet with a simple 12W panel, about .35% of a 220Ah bank, I was able to push two healthy Lifeline 6V batteries, in series, over 15V in the middle of summer.

Don Casey gets it closer when he calls for 0.3% in panel current for the 20 hour rate, yet I know from experience that the 12W panel will push those Lifelines over the "safe" voltage of 14.4V.

West Marine claims 1.5% in current of 20 hour capacity, Casey 0.3%, Calder 0.5% you then run into statements like those below with zero qualifiers by folks who actually sell them:

Sunshine Solar
Do I need a charge controller?

We recommend that charge controllers are used with 15 watt solar panels and above. This will ensure the battery is not overcharged if the solar panel is connected for any length of time with no charge being drawn.

Not a single qualifier other than a panels of 15W or less don't need a controller......

Or this from Photonic Universe a solar reseller:

As a rule of thumb, it would be safe to use 5W solar panels without a regulator with batteries starting from 50Ah, 10W starting from 100Ah battery capacity.

There are plenty more examples out there so who is a DIY to believe...?

Simple answer is to use a controller.....