It seems to me, from reading the various documents on the political and cultural structure of the Empire, that "honour" has a lot to do with living up to public expectations, and fulfilling your promises. If you, as an Imperial citizen, promise to do something and find yourself unable to do it, you have lost honour - you've let down your family, your patron, your clients (if you have any), the Empire as a whole. Incurring a debt you fail to pay off is just one way of losing honour, though it is the main course of dishonour for which Imperial Slavery is the expected recourse.
I would imagine, for instance, that divorce is dishonourable in the Empire - you've promised to marry and stay married to someone, and you find you have to break that promise. Yet an Imperial divorcee would not feel obliged to sell themselves into slavery - they'd merely have to stay single for the rest of their lives, since no honourable person would willingly choose to marry someone who had already proved themselves dishonourable in marriage.
This whole concept of honour is entirely self-imposed, from the point of view of the citizen declaring themselves dishonourable, rather than a top-down judgement of dishonour from your superiors. But I would imagine that the concept is thoroughly integrated into Imperial cultural propaganda, entertainment and education, so one can debate exactly how "voluntary" the acts taken to alleviate dishonour are, when the citizenry has been bombarded with these concepts of honour from birth.
Honour cannot be self imposed, then it becomes personal morals.
Honour relies on shaming from the community as a whole., when you are not living up to their standard.
If you are conforming to personal morals, an internalised code, then attempts to shame should have no effect on your decisions as you are secure you are making the right choice by your won moral code and not dependent on the approval others for your choice of actions.
Like the difference between shame and guilt.
Guilt is when you feel bad internally for you actions as they don't live up to your moral code
Shame is when you are shunned by your peers for not living up to their consensus of Ethics in place.
Honour relies on shame not guilt, honour is external only.
You cannot say you have honour merely because you follow your own moral code, if that code goes against the social expectations and mores, as you will be shunned and they will try to shame you.
Interestingly we can see two examples of this in RP on the forums.
Federal Players try to shame imperial players for condoning Imperial Slavery.
An example of one group trying to impose its ethical code upon another by shaming them, thus appealing to a sense of honour or lack there of.
But since the Empire and the Federation are rivals and not peer groups then the attempt to cause loss of face is lessened as the shaming is from the Federation ethics applied to Imperial citizens, so there is no loss of honour in not conforming to a foreign ethical code.
The appeal should be not shame but to the individuals own moral code, to make them feel guilty rather than ashamed.
Another example is the Children of Liberty, in the Alliance who try to shame the Alliance for allowing non Democracies in its ranks.
https://community.elitedangerous.com/galnet/uid/55c1d2b89657ba00210d630d
So they are trying to Shame the alliance and cause it dishonour as the Alliance does not conform to the Ethics of the Children of Liberty.
Again this fails as the Alliance has its own Ethical code, so be they are not the same, there is no dishonour in not conceding the Children of Liberty's demands.
In fact the Children of Liberty are directly opposed to the ideals of the Alliance, as the Alliance of Independent System as set up to oppose external powers imposing their ideologies on Alliance members, and as per the Frontier First Encounters Manual, any Member of the Alliance must be a signatory on matters of basic Human rights and all citizens of any Alliance Member has the same rights anywhere in the alliance, so those who are in non-democracies do so out of free association. The Children of Liberty demanding all Alliance states be Democracies or be expelled, is in direct opposition to the founding principals of the Alliance
So again we see an attempt to Shame and cause a loss of Honour, by one group attempting to impose its ethical code on another, and hence the attempt at shaming fails, and just as the Children of Liberty doesn't recognise the Alliance Ethics and founding principals, then it they will not be shamed in to accepting them either.
Honour must only be external, not internal, also but only from ones own peer group.
So the concept of honour is alive and well, where ever there are attempts to get people to conform to group ethical code (group ethical is really a redundancy as Ethics is from Ethnos or tribe, it is the rules of living in the tribe so to speak) by shaming tactics.
I disagree Monk that a culture is honour is a culture without laws, as there were plenty of honour cultures with also codified laws.
Rehabilitation is only a recent concepts and unconnected with honour and law but the move away from laesa maiestas and the rise of humanism