for example, the most highly evolved plants reproduce by means of seeds, and, in the most advanced of all plants (angiosperms), a reproductive organ called a flower is formed.
The existence of higher mammals and higher animals implies the existence of lower mammals and lower animals, and therefore possible devolutionary directions.
I suggest you read the wikipedia link? The terms higher and lower are, as far as I understand, mostly just there for classifying the amount of complexity present in an organism - there's not some "these organisms are better than these other ones" thing going on.
Unless you mean something entirely different than what most people mean when they say "devolution", what you are referring to is just evolution. The same way that "reverse racism" is just racism.
evolution can be both 'progressive' and 'regressive'. [...] if a population deteriorates genetically it certainly is something like 'devolution', and this article completely ignores this issue. [...] deterioration, misconceptions aside, is a real thing, and we need to stop giving people the impression that it is only a 'fallacy'.
I said "Devolution is a nonsense concept" because, as I stated before, what is referred to by "devolution" is just evolution. The term, as used commonly, implies some sort of objective heirarchy to evolution, and although organisms may get labeled with terms describing their complexity, that does not mean that one has somehow "devolved" if it evolves into an organism with less complexity. It has just evolved.
Edit:
There's not much disagreeance on the page. There are people talking about using the term to describe something that actually happens, but they aren't talking about what most people mean when they say "devolution".
http://www.google.com/search?q=%22higher+animals%22
The Encyclopedia Britannica mentions plants that are more highly evolved than others: http://www.google.com/search?q=%22highly+evolved+plants%22
http://www.britannica.com/EBchecked/topic/463192/plant
for example, the most highly evolved plants reproduce by means of seeds, and, in the most advanced of all plants (angiosperms), a reproductive organ called a flower is formed.