read over your post and find that for yourself. I will however say a few things on the general topic.
One of the reasons that grammar and spelling are important in communication is because of accuracy and shared understanding. If allowed to just go on and on it can become a slippery slope until you get to the point where your attempt to communicate an idea etc. is misunderstood by the person you are communicating the idea to and that leads to multiple problems. One example is they could confuse and misinterpret your intended meaning, another is they could act upon that confused interpretation thinking that they understood your meaning when in fact you communicated poorly.
The responsibility for clarity is on the part of the person originating the communication. To that end we have normally understood and accepted rules for grammar, spelling etc. While you are not perhaps overly error prone to the point of being misunderstood there are many people who try and speak or write to convey a communication and it is such a horrible mess that it is barely understandable and in many cases requires clarification over and over. I've dealt with people like this in business and over the phone.
This can be particularly important when making comments or posts about politics, business, finance, family etc. So it may irritate people that someone corrects them, and maybe that can be done more diplomatically sometimes, but garbled messaging or thinking it doesn't matter is irritating also.
We should all understand that almost nobody is going to be perfect and sometimes a simple error doesn't affect the message as might be the example of using "a" instead of "an" but can be more critical when talking about something being singular or plural or having the proper tense. I am guilty myself of typos or typing a thought so fast that I leave out a word. But I do try to go back over my things and edit them.
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