It bugs me too when I've posted something and later someone else says virtually the same thing. And yes, it's even more irritating if they get a response and I didn't, especially if it's about a link we both posted. But this says more about me than anything else tbh and I just try to let it go.
However, I do agree with POGS about taking the time to read through post about more serious subjects. My reasons for doing this is to respect the other posters and not look stupid.
Re posting a reply after reading through several pages, what I do is type my reply in stages on a notepad app and then copy and paste it in the reply box. Easy peasy.