Ok, so as I understand it, that is a wear line where the seat post used to set. You've raised the seat post, then touched up the wear line with paint a year ago.

So, the cracking and discoloration is due to a bad touch-up paint job.

But, there may also be FLEX at that point which would also crack the paint.

You've ridden your bike some and haven't impaled yourself which is a good sign. You did have it inspected a year ago, but not recently. Do you still have photos of it before the botched paint job?

You could take it back to the shop for re-inspection a year later. However, put it back up on the web. Take good photos, and explain the situation the best you can do (pre touch-up would be good too). Perhaps it shouldn't affect the sale price, but I have no doubt that it will affect the final price as it just looks suspicious.