You see a little oil where the case halves meet, but I put dye in my oil, used a UV light, and this seam glows bright green, while I didn't see anywhere else that lit up very much.
It just seemed like that was oil sprayed off some moving part.

I have been trying to track down oil and transmission leaks for a year or two. I needed to replace 3 quarts of oil and 3.5 quarts of ATF in 5,000 miles!
I think that I saw some ATF on the exhaust, but just a few drops.
Since I don't see that leak I have tried to focus on the oil. I keep cleaning the engine and trying to find the leak(s). The dye was all over the oil pan, but not above it.

A mechanic verified the oil pan gasket was leaking, so I replaced it, but the leak continued.

Another mechanic pointed out oil behind the valve cover leak, so I cleaned it, and didn't see new oil.

He immediately suggested that my rear main seal is leaking, which is possible, but as far as I can tell oil is dripping onto the transmission where the case halves meet and running down.
Wouldn't a rear main seal leak from the transmission, not onto it?

My car had some recalls, so I took it in for that, and asked the dealership to find my leaks. The mechanic didn't notice any ATF, but said there was oil all over the bottom, and there wasn't Hondabond on the corners of the [Felpro] valve cover gasket, so obviously I need to replace that, and they will put Hondabond on the corners. There isn't oil below the gasket!

He sent me a video showing oil on the mating surface of the oil pan and all over the bottom of the car, but he said he couldn't see where the leak was, but it must be the lack of Hondabond on the corners of the valve cover gasket!

Someone mentioned the distributor seal.

Are there any other likely culprits?

I spent hours trying to research what could leak onto a transmission and just found results about transmission leaks, but nothing useful.

When I tried to figure out how to diagnose a rear main seal leak I just found ads from stop leak products.

From where do you think it is leaking?
Thank you very much! Have a great day!

 

Did these oil and/or atf leaks start happening after any work on the car, or an accident?

The answer to both the engine and AT leaks is that you will have to find them. My best advise is to clean off all the old caked on oil/atf as best you can. Next get some athlete's foot powder spray and spray it as much as you can on the block and transmission. Hopefully you can trace the highest point you can get oil leaks.

For the engine oil leak. You can look for evidence of the oil leak. Pull off the distributor cap to see if you have any oil inside the distributor. The distributor to cylinder head has an o-ring that can leak. The valve cover gasket also look to see if you have oil in the spark plug tubes. The oil pressure switch on the firewall side of the engine is a culprit. See if there is oil inside the boot to the oil pressure sending unit. Beware, that rubber gets brittle over time, so it can crack like plastic when trying to remove. An old spark plug boot could serve as a replacement. Oil filter housing is another area. Also, oil leaking from behind the timing belt cover. Oil pan gasket is another possibility. If you have a vtec engine, then the vtec system could have a leaking gasket. The rear main seal should leak out of the bottom where the engine and trans meet shown in your pic. I know there are a lot of items, and I do not recommend replacing any of them until you find evidence they are leaking.

I haven't read many transmission fluid leaks on here. It is the same process, clean and spray the foot powder to help locate leaks. Look at any solenoids on the transmission and sensors. I'd look at the transmission cooler lines as well.

Hopefully the powder will help you track down the source of your leaks.

 

I had a transmission CEL in April of 2021, drove straight to a transmission shop, and the guy gave me an estimate without even checking my fluid.
I had checked my fluid. It was low, but it was still on the dipstick.
I topped off the fluid and the CEL went away.
I immediately bought a Camry, but kept driving the Honda because I enjoyed it more.
I just checked the fluids more often.
I had been trying to track down an oil loss, but I hadn't seen a leak, or any puddles.
I lent this car to a single mother I knew who had recently been homeless. She was looking for a place to live and a vehicle. I told her to drive my car, find a place to live, and then worry about transportation.
She refused to return my Accord for 6 weeks and she had driven 5,000 miles. I had just changed the oil and topped off the fluids.
The car was dirty and low 3 quarts of oil and 3.5 quarts of ATF.
Motor oil has dripped off the transmission ever since, which I certainly hadn't seen before.
We haven't talked since.
I don't think she caused any of the leaks, they just got worse while she was driving the car, although it seems likely there was some damage from driving with low fluids.

I have spent hours under my car, cleaning the bottom of the engine.
I used the high-pressure spray at the carwash, sprayed with P21S carwash, sprayed degreaser, scrubbed with detergent and an old toothbrush, and hosed off after each step with a high-pressure nozzle.
Most recently I steam-cleaned what I could.
I have used foot spray before and I have dye in the oil and ATF.
As far as I can tell oil is dripping onto the transmission where the case halves meet and running down, so I need .to look on top, but I needed to leave my car at the dealer for recall repair, and I got a ride 3.5 hours home.
As I understand it, if there isn't pooling oil on top of the transmission, I need to clean it the best I can, drive, and check for leaks. The most likely culprits are the valve cover, head gasket, and distributor seal, oil pressure switch, oil filter housing, timing belt cover, and VTEC solenoid.
I know that you wrote out some or all of those, but I found the first few before rereading that part of your response, so now I have a checklist!
I recently replaced the oil pan gasket. There is oil on it again, but the dealership said it is coming from elsewhere.

Of course, he also said that he cannot pinpoint the source, but kept saying I don't have Hondabond on the corners, so I need a new gasket with Hondabond.
No Hondabond, but no leak!

I don't own ramps, just a jack and stands, but I think that I will buy some ramps, drive up, check out those various places, and I still haven't located the leak, spend a lot more time cleaning!