Hmm. Yeah, you're right they use the letters interchangeably, for the same two sounds. Interesting idea about dialects -- the rule could very well be only in some dialects, but it's certainly present in the one they write all the books about (West Saxon, maybe?) and you can definitely see its reflexes in ModE; the voicing rule would be why we have plurals like wife/wives and leaf/leaves (the vowel used to be there to condition the voicing and later fell out; the plural morpheme gets pronounced /-z/ due to the usual ModE plural allomorphy rule.
I wouldn't say that it's necessarily predictable without being told about it, either -- sure, intervocalic voicing is ridiculously common cross-linguistically, but this is more than just intervocalic and it's also not a rule we actually have anymore in ModE. Just like I wouldn't expect a ModE speaker to naturally know how to pronounce pre-Great Vowel Shift words even though trisyllabic laxing (e.g., sane/sanity) preserves the pre-GVS vowels. Bits of lexicalized phonology don't mean much.
*takes off phonologist hat, puts on syntactician hat*
And I promise that OE word order, unmarked, is verb-second. Sure, there's flexibility, because it has some inflection, and in poetry more so, as well as in things like the NT that are likely to be directly translating, say, Greek, but really it's verb-second like a proper Germanic language, I promise:
soþlice hit wæs ofer stan getimbrode forsooth it was over stone built
(sorry, I lost my dots and macrons) which is from, uh, somewhere in Matthew, and a decent example of something V2-like. Sure, with sentences with no auxiliaries are gonna look a lot like ModE, but as soon as you throw in auxiliaries you see you've got a very Germanic word order. (Current English word order is totally the fault of the French. Stupid Norman conquest.)
*takes off syntactician hat, runs to catch bus* I can geek more later if you like.
no subject
I wouldn't say that it's necessarily predictable without being told about it, either -- sure, intervocalic voicing is ridiculously common cross-linguistically, but this is more than just intervocalic and it's also not a rule we actually have anymore in ModE. Just like I wouldn't expect a ModE speaker to naturally know how to pronounce pre-Great Vowel Shift words even though trisyllabic laxing (e.g., sane/sanity) preserves the pre-GVS vowels. Bits of lexicalized phonology don't mean much.
*takes off phonologist hat, puts on syntactician hat*
And I promise that OE word order, unmarked, is verb-second. Sure, there's flexibility, because it has some inflection, and in poetry more so, as well as in things like the NT that are likely to be directly translating, say, Greek, but really it's verb-second like a proper Germanic language, I promise:
soþlice hit wæs ofer stan getimbrode
forsooth it was over stone built
(sorry, I lost my dots and macrons) which is from, uh, somewhere in Matthew, and a decent example of something V2-like. Sure, with sentences with no auxiliaries are gonna look a lot like ModE, but as soon as you throw in auxiliaries you see you've got a very Germanic word order. (Current English word order is totally the fault of the French. Stupid Norman conquest.)
*takes off syntactician hat, runs to catch bus* I can geek more later if you like.