I there are leaks in the attic, major staining on the shingles, places where shingles have been replaced with discolored shingles, or the lower sections of the roof getting a lot darker than the upper section, these are indicators that the shingles are nearing the end of their life and will be a red flag to appraiser. 

My tenants love that aspect and I appreciate them pointing out every little thing from a whole in the fence that the bunny's get through, to discoloration in the caulking around their tub. 

While re-reading the property description, I noticed the above note: 'Property may have discoloration', and I have no clue what this means.  

"Yesterday we were cleaning the garage and noticed some discoloration on the ceiling.

The backyards of the surrounding neighbors though, didn't look very nice. 3 out of 5 had sheds in their backyards that looked like they were falling apart, and one of the sheds was almost as tall as the house. 2 out of 5 also had a canopy/tent type thing and they both were discolored with holes in them, but they were still propped up.

If there is discoloration in the wood pores then you can do a light sanding, HEPA vacuum, wipe with the soap/water solution, allow to dry and HEPA vacuum again.  

They are telling you there was a "discoloration, that may, or may not, have been mold" and letting you know that no mold remediation was done, in other words....."

Roofs often get discolored just because mildew (or whatever it is scientifically?)

The appliances look 5 years old in 1 years time ; are scratched up ; carpets were not in great shape to start but are very dirty / dis colored now.

Mold that has been there awhile smells and discolors the surface.