I could be wrong but here’s what I think – when someone displays a lack of skill in spelling or speaking, it doesn’t actually make them an idiot or take away credibility. There are two problems however: one is simply that if it’s really bad, people won’t understand what you’re trying to say. If it’s at that point, something should be done to bring it up to par.
The other problem is that unfortunately the metzius is that many people will view you as an idiot (which, in my humble opinion, stems from a craving to feel superior to others). If you don’t care how people look at you, fine. If you do, you should work on your skills.
Also, I feel that certain people here are being quite obviously self-conscious on this thread specifically, and making much greater efforts than usually to use bombastic speech and to sound sophisticated and “cultured.” That’s just the sense I get.
Lastly, I strongly agree with yitzchokM. This is a blog for crying out loud