Where to start... meh, I'll just take it in the order it was written in the first place.
Shienvien said
only removing the heart or head kills, but losing any other organ could be rather permanently extremely unpleasant
Since the time I established this all the way back then I've actually expanded upon the effect of removing of removing parts of vampires, particularly the removal of their hearts and/or heads. Now, mostly nothing has changed in regards to removing organs from before, and carving out a vampire's heart or beheading them will still technically kill them, although this death may be less than permanent on its own. A vampire will die in the sense that it completely ceases to function and enters extreme dormancy when one of these is removed, but in the event that these were returned before the vampire dried out - which would render it irrevocably destroyed - they could be ressurrected. In fact a vampire could be carved to pieces and effectively killed, yet be capable of reanimating to their full strength as long as they were prevented from running out of vampiric blood (the heart is the one exception to this; with it, any blood would do, since a vampire's heart converts mortal blood into vampiric blood).
So by this new mechanic beheading a vampire or removing its heart would actually only incapacitate it; letting it bleed out, burning it, subjecting it to sunlight or stabbing it in the heart with a wooden object are the only ways to prevent revivation (the part with the wooden object makes sense; I was slightly disappointed that no one tried it back at the church so I could demonstrate that).
Shienvien said
although with, say limbs and such, where does what begin or end?
As long as vampiric blood is applied to the outer limit of an injury, the vampire will regenerate that entity to completion if given enough time... that is, if a limb was severed, for instance, a severed bone would extend and rebuilt its own shape, but not any bones past that. In the example you presented with the forearm being cut off at the middle the forearm itself would regenerate to the wrist, completely rebuilding its body up to that point, but not past it; the hand would not regenerate on its own. Other, more extensive entities in the body such as veins/arteries, tendons and so forth would also restore themselves, but only as far as the shape of the body allowed, meaning that in the example above the regeneration of these would stop at the wrist as well, rather than grow past it and create a horrible incomplete excuse of a hand. Removing a solitary muscle as connection points, as you said, would remove that muscle permanently unless it was returned, in which case it would reattach itself. Generally speaking any part cut off a vampire could be returned to it and reattached with the application of vampiric blood.
I realize what this implies and yes, a vampire could technically slowly and unbelievably painfully clone itself this way, by removing incomplete parts of themselves (pieces of bone, muscle, skin, organs, etc. rather than whole ones), keeping supplied with plentiful vampiric blood (somehow) and eventually reassemble the different parts to an entirely new vampire. It would literally take
tons of blood and a very long time to do this, but it is theoretically possible. A vampire having an arm cut off at the middle of the forearm would also present a slight problem if the one wanted to reattach the hand after somehow having preserved the arm for a while and likely having regenerated their own forearm, since both the severed part and the intact one would have its own complete forearm. It would be necessary to sever the hand at the wrist to actually reattach it... or their own arm at the elbow, though I can't imagine why they would do that aside from the greater risk of the severed arm bleeding out compared to their entire body.
Shienvien said
It should be rather hard to tear sizable holes into clothes just climbing buildings...
I just imagined that with the walls of the building apparently being rough enough for a man to climb up and find foothold on, it would also be rough enough to potentially catch and rip clothes, particularly if one was to throw oneself bodily at it. I'm not saying that it would be inevitable, just that it was a possible risk. Besides, the hole wouldn't need to be very big... just a small bit of vampire-skin being subjected to direct sunlight would be enough to pretty much spell its doom, considering that the skin would burst into flames in seconds, which would at the very least be liable to expand the hole pretty quickly.
Shienvien said
I wonder, though, how much would full clouds dampen sunlights' effect on vampires? These only scatter sunlight, but don't really block it entirely.
You're right about that. According to my hastily-executed research on how much a heavy cover of clouds would actually scatter sunlight, I'd estimate that a vampire might last about three or four times as long as usual under these conditions. They would still suffer the same fate, it would just take a bit longer.
