The verb muv means "to join".
There's the Ca'Non sentence:
Qo'noS tuqmey muvchuqmoH qeylIS
kahless united the tribes of kronos
Which actually means "kahless caused the tribes of kronos to join each other".
Right, the tribes join *each other* (and not something unspecified). That is, it means something like {muvchuq tuqmey. 'e' qaSmoH qeylIS.}
And now let's come to the prefix trick.
qanob'eghmoH
I cause you to give yourself something (which isn't specified)
This is like {bInob'egh. 'e' vIqaSmoH}. The thing given isn't unspecified, because {-moH} indicates that the verb acts on the performer of the action. Your sentence (if it's even grammatical) means "I cause you to give yourself."
Also, I don't see how this is an application of the prefix trick. What's the version of the sentence where the indirect object has been made explicit? (For example, {taj qanob} means {SoHvaD taj vInob}. Is {qanob'eghmoH} supposed to mean *{SoHvaD vInob'eghmoH}?)
SanobchuqmoH
I cause you to give each other something (which isn't specified)
If Kahless had said to the tribes, {SamuvchuqmoH}, it would mean the tribes join *each other*. Similarly, {SanobchuqmoH} means "I cause you to give each other" (i.e., what you give isn't unspecified, it's each other). {Sunobchuq. 'e' vIqaSmoH.}
Again, how is your sentence an application of the prefix trick? What's the version with the indirect object made explicit? *{tlhIHvaD vInobchuqmoH}?
taj qanob'eghmoH
I cause you to give yourself a knife
taj SanobchuqmoH
I cause you to give each other a knife
In the above last two examples, seemingly/apparently the prefix trick rule isn't violated.
It doesn't appear to be violated because it isn't being applied.
So, seemingly/apparently we *can* use the prefix trick with {-'eghmoH} and {-chuqmoH}.
Right ?
I can see no evidence for this claim based on what you're written above.