Here's a compelling case that reinforces my reasons for not using a truss rod that adjusts through the soundhole on my own guitars. This is a Washburn Festival Series acoustic/electric/ hybrid. It's not a high-end instrument but it's in excellent shape and it does what the owner wants it to do. Unfortunately an attempt has been made to correct a rising action by tweaking the rod. This guitar has a double-action rod. It seems to have been twisted the wrong way. The action was cranked up close to a full 1/4" before the nut snapped!
The repair cost would come perilously close to the retail value of the instrument. Now. If the rod had been installed the other way - adjustable at the head, then there's a good chance I could have drilled it, hooked it with some pliers and pulled it out. At the very least I would have been able to release some of the tension hopefully making it playable.
Preserving strength around the headstock is a thoughtful design feature, but in this case it has made repair economically unfeasible.