And this was surely even more true in the Middle Ages. We have a country that is, overall, tri-lingual: Middle English, Anglo-Norman and Latin. Out of these, the concept of spelling only seems to apply to Latin. And I just don't understand that. Having consistent spelling, with maybe a few errors, irregularities or regional variants, I understand. Considering spelling irrelevant and variable, I also understand. I do not understand how you manage to speak and write two or three different languages, and yet consider consistency in spelling important only for one of them. Granted, Latin isn't entirely consistent - one might contract 'occupaverunt' to 'occuparunt', or waver in how one wants to notate -oe- - and the vernaculars weren't entirely inconsistent, but overall it still bemuses me how the human brain can preserve such a distinction in their attitude to language.
This post was mostly prompted by a certain entry in the Anglo-Norman Online Dictionary, which is, if a little excessive, not atypical. I think this would be a good moment to quote it:
iluec, iluc, ilucs, ilueches, ilueckes, iluek, ilueke, iluekes, ilueks, ilueques, iluesques, iluk, iluke, ilukes, iluks, ilunqes, iluoc, iluoqes, iluque, iluques, ilux; elec, eleckes, elekes, eleuc, elluc, eloc, eloec, eloques, eloek, eluec, elukes; ilec, ileches, ilecqes, ilecques, ilek, ileke, ilekes, ileks, ileoc, ileoches, ileok, ileoke, ileokes, ileoks, ileoqe, ileoqes, ileoqs, ileoques, ileoskes, ileosques, ileqe, ileqes, ileqs, ileque, ileques, ilesqes, ilesques, ileuc, ileuk, ileuke, ileukes, ileuks, ileuqe, ileuqes, ileuques, ilex; illaoques; illec, illecqe, illecqes, illecques, illecqz, illecs, illecus, illeekes, illek, illekes, illeocqes, illeocques, illeoke, illeokes, illeoq, illeoqe, illeoqes, illeoqez, illeoqs, illeoque, illeoques, illeoquez, illeosqe, illeosqes, illeosqs, illeosque, illeosques, illeouqes, illeouqs, illeq, illeqe, illeqes, illeqoes, illeqs, illeque, illeques, illequez, illesqes, illesques, illeuc, illeucques, illeucus, illeuke, illeukes, illeuqes, illeuqs, illeuque, illeuques, illeuquez, illeusqe, illeusqes, illeusqs, illoc, illock, illocqes, illocques, illoec, illoek, illoeke, illoekes, illoeks, illoeq, illoeqe, illoeqes, illoeqez, illoeqies, illoeqs, illoeque, illoeques, illoequs, illoeqz, illoesks, illoesqes, illoesques, illok, illoke, illokes, illoks, illoq, illoqe, illoqes, illoqs, illoque, illoques, illoqus, illosqes, illosques, illouke, illoukes, illouqes, illouqs, illouque, illouques, illouquez, illousques, illuc, illucque, illucs, illuec, illuecqes, illuecques, illuekes, illueq, illeuqe, illueqes, illueques, illuesqes, illuesqs, illuesques, illuk, illuke, illukes, illukis, illuks, illuoqes, illuoqs, illuqe, illuqes, illuqs, illuques, illuqes, illusques, illux; iloc, iloces, iloche, iloches, ilocq, ilocqes, ilocs, iloec, iloeces, iloeches, iloecques, iloek, iloeke, ilokes, iloeqe, iloeqes, iloeqs, iloeque, iloeques, iloesqes, ilok, iloke, ilokes, ilokis, iloks, iloqe, iloqes, iloqs, iloque, iloques, ilouc, ilouke, ilouqes; ylec, ylecques, ylekes, yleok, yleokes, yleoqe, yleoqes, yleoque, yleqe, yleque, ylesques, yleuk, yllecques, yllekes, ylleoqes, ylloqs, yloc, yloec, yloeques, yloques, yloucus, yloukes, ylueqes, ylueques (hiluk Rot Parl1 i 389; ieluec S Audree 1512; ileu Anc Test (E) 7359; iley Durham i 174; ilioqe Rot Parl1 ii 87; illence (l. illeuce) Negotiations 102; illoik BOZ Cont 100; ilokis ROUGH 1; illoiques Edw Ring 66; illonqes (l. illouqes) Stats i 197 (var.); illonquez (l. illouquez) Readings 215; illovecques (l. illouecqes) Foedera iii 488; illus Rot Parl1 iii 91; iluekas Becket 4621 (var.); iluch Anecdota 13; ylooques Art 852)
adv. 1 (local) there, in that place; (local) (motion) there, to that place 2 (temporal) then; then, in that case;
Honestly. Did court scribes hold inter-county tournaments to see who could come up with the most obscure new ways to spell it? All that copying work must have got pretty boring, after all.
So, my conclusion is that the initial question rests on a false assumption. Latin and the vernacular(s) did not occupy the same space in most people's minds, and so they need not match in their rules. Perhaps Latin was learned from the page and largely stayed on the page, while written Anglo-Norman and English were considered a transcript of speech, rather than absolutes in themselves. Latin is a set of rules and signs, almost entirely self-referential: the vernaculars grow and change and steal and adapt. Latin was an internationally recognised code and had to remain consistent in order to BE Latin, but the vernaculars belong in the mouth of each speaker.
And, because I am worse than a dog with a bone: see? Not a real language.
 I've yet to see a dog pay any attention to a bone for more than an hour tops. Solace buries hers within five minutes then runs around stealing the other dogs' and burying those.
Bonus points to anyone who recognises the phrase mangled in the title.