The message
from Tony Morgan contains these words:

In message , Paul Kelly
writes
Why are you challenging what has long been "best advice" for planting
clematis?

Clearly you do not bury all the mature stem but the site advice:

Plant deeper than the original container - not necessarily 2 or 3 inches
deeper, but as much as it takes to get at least one other set of leaf nodes
below the ground. We have done this since the plant was a cutting, and it
has been potted on at least three times since then. Do it once more!

is sound.

Then I'm afraid we must agree to disagree.

I've been growing clematis for 47 years, I can assure you that if you
plant a set of leaf nodes below the surface and you have a wet spell
within a week or so, then you can expect to get rot and lose the plant -
not necessarily but there's a good possibly..

I've always planted clematis deep for the same reasons Rachel has
given, and find they do very well; even though they invariably have a
wet spell soon after planting. I live in the extremely wet west of
Scotland; rainfall at least 70" pa and rising.

Janet.