A common factor I can relate is the fact that it's either one user or few users from a non-english speaking country that is usually creating this threads. You will rarely see this kind of posts in other forums because they don't have much attention and needs in other forums so since this user/users knows the forum better that's why they keep trying with different usernames.

That's all I can relate with this terrible grammar users

Well not all users here have english as their native languange also we dont know the particulars if they did studied english on their school or maybe they arent just as fluent like others.

Well they can improved but having the talent to do cryptography and deeper thoughts on that isnt easy.

I would speculate those people come from same/similar region where English isn't their primary language. But rather than how they speak or write, i would worry whether they talk non-sense, perform scam or share malware. Moderator gmaxwell used to post warning on such threads, for example,
https://bt.irlbtc.com/view/5280670.msg55550454#msg55550454
https://bt.irlbtc.com/view/5375382.msg58639160#msg58639160
https://bt.irlbtc.com/view/5209950.msg53411323#msg53411323

Let me put it this way. Being poor in communication (English) does not have any limitation on people who have a skill, talent, or are tech-savvy. English is a means of communication and not all countries speak British English or American English fluently.

Actually, the last time I checked most of the nerds and crypto genius who are interested in the blockchain and cryptographic are mostly from Asia, Russia, and Africans. So i do not expect the best English from them.

If we are being completely open minded then that would probably be the most obvious explanation  or speculation (they are people that come from or reside in the same region where English is not the primary language), however the secondary possibility that comes to mind is that maybe all of those particular accounts could be operated by the same person.

Yeah that would be my guess too because the main thing is the knowledge they are trying to pass across and if they've effectively done it but the grammar is not aligning, it's not their fault most times since just like you explained, it's not everyone who is a fluent speaker of English.

Sorry, but judging someone for using poor English isn’t good. There are many users here whose first language isn't English, but they are very skilled at what they do. In the IT world, for example, you don’t need to be great at English to program, but their contributions are huge. So let’s not be judgmental, because for me, English isn’t my native language either, but I try to communicate so that everyone can understand. Remember, this is a big community with people from different countries, so we need to be understanding. As long as it’s understandable and readable, I think that’s fine.

You have tried your best for the contribution but I will not call those people as terrible grammar users because English Language and programming language for writing script are two different things. We all I know that English is a L2 in 98% in the world and the L1 is 2%. Even the people of England speak another language and tell today the origin of English is still unknown by linguists. Anglophone and Saxophone are still dragging the origin. Now if non English speaking user used the language to write, it will make mistake because English is all about rules and it is not easy for a non English speaker to follow all the rules and when they are using it and since the language is not from their origin, they would mistake either in pronouncing the English words or writing process, and once it happens like that, they would like to use or mix them with their native language and the English became terrible for the English Speaker.

Even in this forum the way The Sceptical Chymist twist words that is different from others which I have seen or known, he follows the rules of grammar and non English speakers can't do that. So when such person is using it to write script, it would becomes a blunder to the English accuracy person. Therefore the puzzle hunters are terrible at that English because they don't know the rules to use.

Of course! You can't communicate properly if you don't speak the same language.

You can't focus on the content if the sentences don't make sense.

I'm pretty sure that saying wasn't created with online forums in mind.

In my experience, most people with terrible English aren't "skilled" at what they're posting. And other skills don't really show online.
In most cases, I find the Activity/Merit-ratio to be a reasonable "measure" of someone's "forum skills".