Anyway, do you have an example of text in which this function causes
point to return such problematic values?
The only example I have is the one I described already, as best as I could. A user reported it to me, i installed clangd, and I reproduced it very easily.
If you could consider installing clangd then running that ready-to-use recipe, I'd venture to say it's the easiest way for you to understand the problem.
> Why do you have to use move-to-column instead of forward-char?
>
> I don't remember! Is it exactly equivalent if you're standing in the beginning of the line?
Yes, if you have only text in the buffer (no images etc.).