Being annoyed is no crime anyway and I have no problem with you giving your opinion and think you have made some valid points.
I do like to have some goals to motivate me to learn. Maxing known words stats is one way to do it, even though it´s limited and mostly helps with reading ability, less with writing ability and much less with speaking and listening ability. You can lose yourself in the word count (or other stats) to a degree and that can indeed be counterproductive to you learning the language as best as you could. You could neglect speaking, listening, writing for sure. Then again there´s the question of what is available to you. Not everyone who has LingQ necessarily has the same options of interacting with others, from Corona problems, to bad sound on your computer to slow internet connections etc.
I agree that you can´t compare word counts between people to accurately know which one knows the language better, not even as far as reading goes. If someone is already fluent in a language or far along in it at least, but haven´t been reading it on LingQ for long, the count is obviously going to be too low. Same thing if they are only using LingQ a bit here and there and mostly learning through other methods. Also, like you pointed out, ppl will have different ways of marking words as known. Some are more eager to do it, some ignore names, foreign words, compound words etc. while others add them. The occasional weirdos even cheat and just spam in known words. Thus if you want to compare word counts between people to have an idea who is more advanced in reading, you´d need to know other things about them (sometimes their other stats would give an idea) and even then the comparison would be a rough estimate.
Even with that, I think people who have honestly gotten to high word counts, 40K+ are very, very likely to be highly literate in the language. If they have 30K+ in multiple languages, let alone very high numbers like 50-70K, without cheating, they are highly likely to be skilled language learners and could be called “successful”. It interests me which users have such stats for a number of reasons. Who are these people, where are they from, what languages did they learn, what drives them, are some cheating? … and so on.
This link you posted is somewhat off actually. The word count (as long as you actually work to achieve it) does to some degree correlate positively to one´s ability in a language (at the very least the ability to read it), where having better light in a place where nothing is to be found correlates 100% negatively with finding things. If I had, say, the goal to learn Ukranian on LingQ, but only read Spanish instead because there is more material in Spanish, or wanted to learn Faroese and would still use LingQ to do it when it doesn´t have Faroese, because I think LingQ is effective to learn languages in general, then the comparison in the story in the link you posted would hold much better.