Originally Posted by
Some person
Most train tickets in Europe are subject to the
GCC-CIV/PRR terms of use.In other words, if you don't claim your seat within 15 minutes from departure from Paris, your reserved seat may be sold to someone else. I think that you are still allowed to travel, just without the right to sit down during the journey.
Unless the train company's own terms of use states otherwise, assume that the GCC-CIV/PRR terms apply.
I get this but unlike boarding an aircraft no one checks your ticket upon boarding to make sure you actually make use of that segment. I'd say it's safe to hop on mid-journey.