Nautile / Charles,
You said,
I think that some knots ( oriental ones) were deliberately, from conception, ornemental ( see ikebana, origami, haïku/haïki...for example of japanese aesthetic preoccupations - I have less "contact with the other civilisations in Orient).
Though one must never forget that it could have been a clever disguise under which were stated social status, ability status...
Let us take a specific example of a knot name from the knotting traditions of Japan. The knots known by this name might be considered, by many, to be ornamental. The knot name is
ume musubi. It could be translated as "plum knot" or perhaps "plum flower knot".
There are several different types of knots (different knot structures) with the name
ume musubi. What they have in common is that they are symbolic of the plum flower. What they have common, in form, is five rounded loops - this is the key to a knot representing the plum flower (1).
The
ume musubi is tied, in many applications, to reflect the characteristics associated with the plum tree and its flower; NOT to represent the flower in and of itself! For example, two possible characteristics would be: it is the first flowering tree (festivals are held for the flowering), and that the plum tree flowers in May/June.
A large tassel hanging from of float could be tied with a
ume musubi in the middle of the cord. This knot would be read (from its association with the plum tree) as first growth, new beginnings, new opportunities. To read this knot as purely ornamental may be a indication of illiteracy!
In the Japanese tea ceremony, a fabric bag might be tied with an
ume musubi. That bag could, for example, contain a clay container (pot) holding the tea. If the month is May, in harmony with the time of the year, the host may have choosen the
ume musubi.
That knot (
ume musubi) is in harmony with the time of the year since the plum tree flowers in May.
The knot on the "tea bag" and the knot on the tassel are different knots. One interpretation of the reason for different knot structures of the
ume musubi could simply be the characteristics of the material in which it is tied and the physical characteristics of its application.
The who, what, where, when and why of a knot name may open a whole new world (domain) of knowledge. In fact, the 5 W's may be as interesting, if not more interesting, than the how.
Perhaps I should think of copying this into a different thread as you suggested.

Cheers - Brian.
(1) Examples (there are more unique structures) to illustrate the five rounded loops are shown here:
http://park.org/Japan/Kyoto/lib/himo2.htm .
Also the
ume musubi is shown here:
http://full-circle.web.infoseek.co.jp/mizuhiki/musubi.html . They are the knot shown in the third row, second knot and in the fifth row, first knot.