Re: blink-cursor-end sometimes fails and disrupts pre-command-hook

[Richard Stallman]

    i would really, really, *really* have liked to backtraces to help
    track this down, but emacs backtraces are useless for that by design.
    you have to know where to put them to get the backtrace from an error
    at that point.

I do not understand that sentence.  What do you mean, "put them"?
What do you mean by "where"--what is a "place"?

      however, i can't understand not having a mode -
    eg, with a `debug-on-error' style variable, eg
    `retain-backtrace-on-error' - for retaining backtraces on any error,
    to be replaced when the next error happens.

We could do that easily, I suppose, but could you explain
how it relates to the problem?