I still think Bentley could be wrong. My old Chilton specifies 15-25 ft lbs for the three 13mm strut mount nuts. It specifies 90-100 ft lbs for the 15/16" strut rod nut. Haynes lists 18 ft lbs for the 13mm strut mount nuts but does not list a torque spec for the 15/16" strut rod nut. Some bricksters have also posted that the 700 series strut rod had a torque spec of something like 110 ft lbs. It stands to reason that the 200 series strut should be similar. 15 ft lbs doesn't seem like much for that fastener, IMO. One guy posted that he thought it should be "one of the highest torque value fasteners on the car". At any rate, it should be tight, and should not clunk. If 15 ft lbs gives you that, so be it.

And yes, on my wifes '88, the clunking was caused by a reusing a worn gland nut which wouldn't hold. New struts and gland nuts solved that problem. This morning, I installed new struts in my '92 wagon and had a slight clunk from the right shock tower on the test drive. Tightened the strut rod nut with an impact wrench and no more clunk.
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'92 240 wagon, 268k, '88 240 sedan 280k