Originally Posted by softreset

The 2-series & 4-series Domanes have a seat post, the 5 & 6 series have seat masts. Sounds like the bike in question has a seat mast. I've had a band of electrical tape mark my saddle height on a 5-series Domane for almost two years that has come off/been replaced numerous times without any issues.

Sounds like the tape was defective.