User blog comment:FairyRaven/Exceeds and Earth Land Counterparts/@comment-4829046-20120820134427/@comment-904888-20120822003848

Like I said before, if 'advancedness' of a DS is enough to trigger an inherent Motion weakness in a DS, so far everything makes sense:

1. Natsu was advanced from the very beginning enough to suffer motion sickness from MOVING vehicles or being jerked rapidly (as in the Key arc, when he had motion sickness when he was rapidly jerked).

2. Gajeel wasn't as advanced as Natsu (again, strong evidence to support this, when Natsu had his strength replenished, he was able to top a replenished Gajeel without much trouble), so he didn't suffer Motion weakness before the 3 month training

3. Wendy would be unlikely to suffer it at all because of her Troia.

4. Cobra didn't suffer it because he was NOWHERE near advanced, because remember, when he used his DS powers, he went into DF, which means that he had to enter DF or else his DS won't do any significant damage.

5. Laxus knew about the inherent DS Motion weakness, hinting that he too suffers from it. He is certainly more advanced than Cobra for being able to use DS magic without needing to enter DF (at least advanced relative to a normal Gen II DS). Although it is entirely possible that he either just knew about it, or he deducted it on the spot during the Chariot event.

6. Lacrima has nothing to do with being Motion weak or not, since Sting also suffers from it.