There is something in E following an O that prevents the tongue from naturally glide, so you would want to put a Y in Dostoyevsky
Short-long distinctions do not exist in Russian (or Bulgarian). Vowels are lengthened for emphasis. "Лук" is pronounced the same in either sense. I did not know that they existed in any Slav language, thank you for telling me.
In Serbian, лук (onion), is identical to the English "look" (although it is a double "oo" it is pronounced as a short vowel). On the other hand, лук (bow), as in "лук и стрела," the "y" is distinctly long but not quite double "уу."
But you won't find a Serbian linguist who will tell you that there is a long-short distinction, but it is clear as a bell to anyone with half way decent hearing.
Another distinction that is actually sometimes made obvious graphically is "a," such as in the genitive case of "letters" (писамâ) or "in order to give" да дâ.
I seriously doubt that similar differences don't exist in other Slavic languages, including Russian and Bulgarian. They may not be recognized, but they must exist, for all vowels can be pronounced as long or short; In Serbian кост, мост, со(л), etc. are long "o" sounds, while боље, кољиво, коњ, слон, etc. are all short "o" sounds.
This topic is so obscure, even finding Ѣ in Unicode was hard
It is obscure in Russian and Bulgarian, which is why it was eliminated. But eliminating it in Serbian was a major mistake. In Serbian the palatalization (inflection) of Ѣ is a major factor in the division of standard Serbian into two geographical variants, which is why Ѣ was a perfect solution for a unified orthographic standard. Today, many refugees from the western parts of the former Yugoslavia bring with them their western version of the language into Serbia and confuse the kids there.
As said previously, this difference is not trivial. Thus победа is pronounced as побъеда in the western dialect but as побэда in the eastern. The word used to be spelled uniquely as побѣда, but today it is spelled побједа and победа.
Святой, etc., also reflects that duality in Bulgarian. In modern Russian, however, only Я is used as far as I can think of it: священник, святость, посвящение. In Bulgarian, E is used in all words corresponding to these.
But how is святость pronounced in Russian? Isn't is more like svetost' than svyatost'? Why not replace it with a "gliding" E then? :)
Yes, that is what I mean by "gliding". However, in Russian language, it is not necessary to add a Ь in front if it. Isolated E glides already. Ь or Ъ regulate the prononciation of the preceding consonant, rather than E itself.
I seriously doubt that similar differences don't exist in other Slavic languages, including Russian and Bulgarian
They probably existed at some point, just like they existed in Greek. But today, in Russia and in Bulgaria people lengthen and shorten their (stressed) vowels, often in an exagerrated manner, to add emphasis and without regard to what word it is, like singers do in songs in any language. This does not add a sillable. Normally, all vowels are pronounced middle-length, for example, И is pronounced as a bit lengthened I in "big" or a bit shortened EE in "beef".
Thus победа is pronounced as побъеда in the western dialect but as побэда in the eastern. The word used to be spelled uniquely as побѣда, but today it is spelled побједа and победа.
I understand. In fact, when the orthography reform was instituted by the Soviets, it was pointed out that Ѣ is not exactly superfluous even in Russian. But the argument sort of died down, quite possible because like with everything during these wretched times, orthography was politicized as well. Ican easily imagine people beign sent to the Gulag for the Ѣ letter.
I did not know my grandmother, but I new my granddad's sister. She was born in 1898. One of the things that caused he to feel bitter even in her old age was the episode when she -- a bookkeeper -- submitted some report to the boss, something she knew was done well. The boss returned it with a red pencil across the front page: "I request that new orthography be used". She did not end up in jail, but that was among her grievances with the Soviet power that she would secretly tell me about, how they made her rewrite (or retype) the lengthy report that was perfectly comprehensible, in fact more comprehensible to the Russian reader, in the first place.
how is святость pronounced in Russian?
It is pronounced "svyatost", as written. When Я is not stressed, it is subject to the same phonetic reduction rules as any vowel, so "посвящение" would not sound differently than "посвещение".