First of all, it seems if one hits the reply button, one can directly respond to a comment by that specific person (i.e., one’s comment will appear below that comment or that thread). The the reader need to scan to find the new comment (especially if there are newer threads at the bottom).
If one just keep typing in the default window, then the comment will appear at the very end of the discussion, as a new thread. Anyone will be able to see that as the latest comment, but then needs to refer to the comment that he/she is responding to.
I am going to try the second option here.
It seems that it would have been better if Tobias typed his response not as a reply to Johnny’s, but to mine (or just typed in the default window to start a new thread and referred to part of my comment so that a reader can trace it). It could take us some time to sort out the best way. One needs to decide which way is better.
Tobias G. said, “Here I have my problem with the mana indriya. The mana indriya is part of the body or located inside the body. Why is it needed to sense kamma (beeja)? As I understand kamma beeja are stored in the mano loka of each being. Why is kamma beeja not directly sensed by the mind or hadaya vatthu?
The same question applies to the mechanism of recalling memories from nama gotta. A brahma in arupa loka has only the hadaya vatthu, no mana indriya, right? If so, how can a brahma sense nama gotta or kamma beeja?”
My response: Bodies of living beings in different realms are formed by the corresponding kammic energies to be able to impart various types of kamma vipaka suitable for those realms.
Since beings in kama loka are born there because of their cravings for pleasures through the five senses, their bodies are formed to be able to enjoy such pleasures, but then also subject to suffering through them. For example, one cannot enjoy sex without body touch (kaya indriya), and one cannot enjoy food without taste (jivha indriya), etc.
But each of those indriya can “go bad” either with age or as results of previous strong kamma (like getting cancer in the body or in the tongue, etc). That is one mechanism of delivering kamma vipaka to beings in the kama loka.
Rupavacara Brahmas are born there because they had lost their cravings (at least temporarily) for olarika (rough) sense pleasures. So, they do not need to sense body touch, smell, or taste and those indriya are missing; furthermore, they can receive rupa and sadda without physical senses.
Arupavacara brahmas have lost cravings (at least temporarily) for even those rupa and sadda. That is why they just have the hadaya vatthu.
These are discussed to some extent at:
Body Types in 31 Realms – Importance of Manomaya Kaya
Gandhabba Sensing the World – With and Without a Physical Body