I just got the keys to my first home last night. I've been through it 4-5 times total and I have never seen this, until last night.
It looks like mold to me but I haven't ever been in a mold situation. The ceiling is not soft or anything. To give you perspective, this is above the living room door where the ceiling and wall both meet. It is a ranch so there is no upstairs, New roof as of 2 years ago.
Do I automatically go to opening it up, asking why the inspector at least didn't spot it, etc?
Yep, no reason the Inspector shouldn't have noticed it and it would be covered by their insurance...put a claim in immediately if not sooner, so they can't try to paint you as creating the problem. Or:
- Miniscule roof leak that the roofer should cover under their warranty
- Roof not vented or not properly vented that the roofer should cover under their warranty
- Damp house (basement or slab getting saturated from poor lawn grading) pointing to where the ceiling doesn't have insulation or nearly enough insulation
- Poor HVAC performance or ceiling ductwork
- Bath exhaust fan not piped to outdoors (again, non-insulated area holding moisture)