Angraecum sesquipedale - is this rot?
 

Finally went ahead and got my dream plant. It has two black areas I'm worried about, one at the bottom near the roots and another halfway up the crown. Its not rot is it? It felt hard, but I'm paranoid after recently losing a bellina to rot.

The plant is missing two leaves in the middle of the stem. You're seeing the dead leaf bases. If the plant is firm it should be OK.

What are your temperatures day/night, humidity and lighting? How are you watering? Was the Phal. bellina in the same conditions?

I use Barrina LEDs. Temperature is 23-25C. Humidity around 50%. I top water around the roots without any dry period. Same conditions for the bellina, which stopped growing at one point and eventually started rapidly dropping leaves. Admittedly the air circulation is not great, but the only other orchid I've lost to rot so far was a Rossioglossum.

If it just arrived, there's probably information you don't have.

The bark is relatively new. If it came that way, the seller may have repotted it very recently. This plant isn't fond of repotting, especially in winter. It may sulk for a while until new roots to begin. That should happen when it warms up. If you have access to a root stimulant like Kelpak that will help.

High humidity isn't necessary for this plant, though it prefers it. People grow them successfully in homes.

Warmth is very beneficial. Until it's growing strongly I would not let it get cooler than what you're doing now.

I don't think the air circulation is bad at that relative humidity.

By the way, this plant will probably be happy outside during your summers, acclimated slowly to dappled shade or almost full sun. It grows in the crowns of palm and hardwood trees over a wide elevation range, from sea level to mountains.

As to the Phal. bellina - It grows well when it is hot and very humid. All Phals. carry more leaves when ambient humidity is high than when it is lower. Phal. bellina isn't a good house plant. Most people don't have high enough relative humidity in their homes to grow it well. It will live and grow at 50% relative humidity and 23-25C but higher would be better.

As to the Rossioglossum - it probably didn't rot; rather, the growing conditions were probably wrong. They don't like to dry out at all. They like high humidity. 23-25C is at the top of their preferred range.