That was answering silly speculation about intentionally leaving worn-out drill bits behind. There are actually workable procedures for drilling around things, but it's far more cumbersome and time-consuming than replacing a bit normally. Those procedures used for things like the drillstring getting stuck due to hole collapse; nobody would do that just for a worn-out drill bit.
The actual way to avoid the problem is by using bits whose design lifetime in the formation you're drilling is at least as long as the hole section you're planning to drill.
Removing many miles of pipe to swap out a drill bit at the end is slow and seems rather inefficient.
Which suggests just leaving the old drill bit somewhere in the ground. But currently doing that would also involve removing the pipe, as to why: https://news.ycombinator.com/item?id=43371776
