Well, in a vertical board I'm always worried that the HSF will fall off, land on the back of the graphics card and cause all manner of fatal shorts (I have seen this happen in person to an old AMD Duron system where a single-clip HSF actually snapped off the dog/tooth it was clipped to, killing an expensive-enough Geforce-256. I've also read enough instances of other people suffering similar issues with Intel push-pin HSFs that I'm now paranoid!)
Since you don't have a dGPU to worry about you can probably ignore it as even if the HSF does fall off, it will swing by the fan cable, and probably come to rest with a grinding fan noise against the heatspreaders on your RAM. There's not much to short against on the topside of a motherboard, it's the backside of PCBs that have all the exposed solder points. Things like plastic slots, heatsinks and solid caps will get in the way of a detatched HSF most likely.
The paranoia in me would:
- twist the suspect post 90 degrees anticlockwise
- pull up to release the black pin inside the white/clear barb
- reset the post by twisting the leg 90 degrees clockwise
- pushing down on the white/clear base of the barb with one finger to make sure the barb's head is through the motherboard hole
- whilst still pushing down on the barb, push the black post down firmly to lock.
Even if you don't hear a solid click, you can be sure the barb is properly engaged if the base was touching the board as the black post went down. OCD satisfied, paranoia and worries assuaged etc