Bah, he's just thrilled that he dug a shaft and missed all the caverns and the lava sea. If you want to go sour-puss, the topic is not that interesting, but I can understand why the author posted it, as one who always manages to hit cavern and have to mess with walling in before the forgotten beasts eat my dwarves.
As of now though the thread is about the kobold who pulled out the sword. That's pretty funny.
For the OP, those kobold thieves have trap avoid, so they won't hit a trap even if they're visible. This is something that should probably influence fortress design. I think it makes most sense to have an entrance corridor rather than an entrance staircase, and that the first room the corridor runs into should be the main barracks, and there should be a dog chained there such that it's impossible to get further into the fort without going past the dog.
There was a thread a few months ago about how a central staircase is a huge security problem and I have to agree with this. Unwelcome visitors can go a long distance very rapidly, fighting on multiple Z-levels is hard, you don't really want to be fighting in your dwarven reactor room or your dining room, and you'd prefer that your legendary armorsmith isn't the one who detects the intruder first.