"Nobody meant anything by it"

This is true. You didn't mean anything by the five days. Your friend didn't mean anything by the fortnight before it. Nobody in the whole thinned list of the last ten years ever decided to let a friendship go. And because nobody meant it, the belief runs, nothing was really done. The silence isn't a slight, so it isn't anything.

The trouble is that intent isn't what a friendship runs on. Contact is. Chapter 8 was about that. A friendship can thin with nobody meaning it in exactly the way a plant can die with nobody meaning it. The absence of a decision doesn't put the water back. What "nobody meant anything by it" actually does is something different, and I think it's this. It answers the question "was I wronged", and it answers it correctly. No. And then it treats that as an answer to a different question, "was anything lost", and it isn't.

Look at how the ending of a friendship by delay actually goes, because it's never a single act. You leave a message a week. They leave the reply a fortnight, partly because a week's silence had cooled them a little. You leave theirs three weeks, because by now there's a surcharge on it. They don't send the next one at all, because the last exchange took two months and it felt like effort at both ends. A year later you think of them, and the stretch is now so long that chapter 6 takes over. Neither of you did anything. Each of you did nothing, in turn, and two unintended silences make an ending as surely as a decision would. The only difference is that a decision would have had a reason, and this doesn't.

I'd rather you saw this clearly than felt bad about it. Feeling bad is a poor tool here. It adds to the surcharge and makes the next reply heavier. What's useful is to notice that "nobody meant it" is exactly the condition under which the thinning happens, because if somebody meant it, they'd have said something, and the silence would have ended one way or the other. The friendships that go this way are the ones where everyone was well disposed and nobody wrote.

Which means the fix is the same size as the problem. Nobody needs to mean anything by a reply either. It doesn't have to be an act of friendship, or a repair, or a sign. It just has to be sent. The friendship that thinned by inches nobody intended can thicken by inches nobody intends, and two lines on a Tuesday is one of them.