It’s not only my posts; it’s everyone’s.
So, i THINK if, when you create your post, you look at it in preview, if you see those weird characters, then just re-type over those letters that came out wrong, then preview again, it will come out fine.
I think what one of the posters above was saying is ... go to one of these sites, and past your text in and IT WILL do the replacing.
So - not your fault or anything ... and yes, happening to everyone. But I think you can control whether your own posts do it ... just by looking at the preview of your post. I THINK it will only do it if you've copied and pasted in text from other sources ...