I was wondering how different people viewed interactions between current and former members in the feudal hierarchy and whether or not people felt that holding a position formerly offered the character any manner of additional respect on top of that with regards to their current posts.
Only when my characters want it to. I.e. I would grant them the old title as a courtesy title, unless the character wasn't considered worthy of the courtesy. That's only if they don't have an existing title, or if I'm listing full titles (normally I just do the most important title of a person, or the most relevant title, but in a treaty or other formal context I would list "former King of Keplerstan").
Also, are non-feudal titles and positions worth anything regards to manner of hierarchy respect or deference in comparison to feudal titles?
Do the titles have any real power, or does my character want to flatter the title-holder? If yes to either question, then of course.
Would you consider former rulers of your realm to always hold the level of respect or deference of that of ruler? (or perhaps they'd be viewed on par as current dukes? Lords? regardless of current feudal holdings?)
They are Royals, which I have always considered to be theoretically second only to the sitting Ruler (with the above exception if my character thinks they are unworthy). But again, actual titles always take precedence to courtesy titles.
What about former rulers of other realms?
Too many other variables. Their relationship with the current Ruler, my relationship with them/current Ruler/realm as a whole, in addition to my usual caveat on current titles.
Do former dukes or lords mean anything to you, or do you only view them by their current ranking? (For instance, My duke character calls all former lords of *his* duchy "Lord ____" instead of "Sir" or "Dame" or "Knight" even if they no longer hold a lord title)
A generic Lord or Lady such and such is pretty standard for me, yes.
Do foreign dignitaries of non-feudal titles hold any particular manner of respect to you? Would you perhaps place any ambassador of a foreign realm with the same level of respect as perhaps one of your dukes? (Address them as "Your Grace, Ambassador _____" Instead of just " Sir Kepler, Ambassador of Keplerstan") I don't, but perhaps some do.
Ambassador Kepler is how I have always done it, but Dukes I just do Duke Kepler as well, so I guess that's the same as how I address a Duke.
Would you grant founders of religion a measure of respect equivalent to a ruler or perhaps a duke regardless of their feudal ranking or if you're a member of their religion? For example, does The Prophet of SA deserve to be treated with a measure of respect by non-SA rulers of at least placing him equal in power as a secular ruler when discussing things? Would his regent deserve the same? (I personally think that all religion founders should be granted that measure of respect, unless you're trying to intentionally anger them)
Hell yes, unless trying to be intentionally disrespectful. I would consider the head of SA to be the most powerful character in the game (note: I know nothing about internal SA dynamics, and for the moment don't care) and treat them accordingly. Prophets of religions with anything beyond two people I'd treat like Dukes, and Prophets of religions with anything approaching a realm (call it a minimum of a dozen nobles and 50K peasants) I would treat as equivalent to a Ruler.
Also, feel free to bring up other cases I missed.
Church Elders are one step down from their Prophet (so Dukes to a King, Lords to a Duke, or in the special case of SA I would consider the Elders on par with a Ruler). Priests of my religion depend on the specific case, but generally at least the level of Lord/Ambassador, possibly more if they are considered to be particularly holy.
