Yeah that's happened to me. Then I woke up.
I have a "makiwara" (wooden striking post) in my home gym, as well as a heavy bag. Legit makiwaras are springy, and taper from maybe an inch and a half thickness at the floor to about three quarters of an inch at the top. Depending on what kind of wood you are using. The point isn't hand conditioning, or breaking stuff - the point is teaching body structure and joint alignment, because the board Springs back at you after a hit. If something bends, you have feedback on where power is siphoning off. I have a thin leather pad on the striking surface to save the skin on my knuckles.
Like a heavy bag, the makiwara has a very different sound when you strike it with snap and a loose arm, rather than pushing through - great feedback on technique. And yeah, it punishes you when you hit with a poorly aligned wrist, which imo is a good thing.
All things in moderation, I don't use it instead of a heavy bag to train power, but for other technical issues. And it isn't exactly a bad thing to get over the reluctance to hit a hard surface with force, because people don't generally wear pads on their jaws when they go to a bar.
Agree with all of it. Also, unless you wear sap gloves all the time, nor can you expect your knuckles and metacarpals to be protected. Even then, a cop I worked with wore the coolest looking ventilated thin leather driving gloves all the time. He made the poor decision of delivering a straight punch to the teeth of someone during a fight and ended up with not only his gloves cut, but his knuckles also. A horrendous infection in his hand ensued. The human mouth carries more potential infection vectors than a dog bite according to some general practitioners I have related this story to.
Thing Two to take away, is to make sure whatever strike to the head or face you use in the event you need to do so, is one that will inflict the most blunt force trauma that causes the brain to rebound inside the cranium a time or so without damaging your hand(s) in the delivery of it. Ungloved straight punches often fail to meet this criterion.
Off the bat, I would have assumed the opposite to be the problem. People failing to consider the double-edged nature of hitting someone in the jaw. Because, you know, movies. But that's a fair point.
Does the makiwara provide feedback re: perpendicular impact with the target surface? Seems like such a small and rounded target would really train accuracy in placing the big knuckles right on target. Have you found it having this effect? Do you throw combinations at a bouncing makiwara?
A suggestion here. But please feel free to take me to task if you disagree Tom.
Get a BoB. Hit it. In reality, it will lack the underlying skeletal structure that can hurt your hand so as to provide negative feedback about where NOT to hit with WHAT.
But if the real point is to get some conditioning from striking, which, as I recall, was the original issue, do not over think any of this.
Otherwise, consider what your underlying purpose is or was.
I suspect that a Bob dummy is the way to go - I made a makiwara because I'm cheap, and traditional. The advantages of a Bob includes realistic targeting for neck strikes etc as well, and a lot more flexibility for footwork and practicing getting off-line and then attacking. Which is all good.
It is possible to do some combination work on a makiwara, but it is not really the best tool for that imo. Though it is good for following a punch in with an elbow from the same arm. If you are interested, there is a really good Goju karate teacher named Paul Enfield who has some great video up on YouTube of his dojo's makiwara work, and the variety of striking techniques they use it for. Me, I train punches, knife hand strikes, back fists, and elbows - it takes a bit of a learning curve esp with knife hand and back fist to learn how to strike so that you hurt the other guy more than yourself. A curve well worth travelling through though, imo.