The B-Greek transliteration scheme at a glance:
B-Greek has from the beginning allowed every poster to use any scheme he/she found comfortable, since we all could usually figure out what text was meant. For those who wish some guidance, a generally accepted scheme has evolved on the List, with two or three matters still not fully settled.
(1) CAPITALS are used when transliterating Greek letters, on a one-to-one basis, reserving lower-case {i} to represent iota-subscript and lower-case {h} to represent rough breathing. No accents, no smooth breathings. And no distinction between medial and final Sigma.
(2) If accents are really necessary, to distinguish otherwise identical words, acute is represented by {/}, grave by {\}, and circumflex either by tilde {~ [preferable]} or {=}--always AFTER the vowel over which it would be written.
(3) A few characters without Roman single-character form are usually done with almost-look-alike Roman characters otherwise unused:
Theta = Q
Eta = H
Psi = Y (Upsilon is always U)
Omega = W
(4) Digraphs (in the usual Roman transliteration) are handled in three different ways to avoid two-letter transliterations, all involving otherwise-unused Roman letters:
THeta uses Q ("look-alike," as above).
PSi uses Y ("look-alike," as above).
PHi uses F (sound equivalence).
CHi uses C (first letter of traditional digraph).
(5) Xi and Chi: There being no single Roman letter for "Xi" other than X, the "look-alike" use of X for "Chi" is confusing, though some use it. And some seem to like to use C for "Sigma." Since S is otherwise unused, and poses no confusion whatever, using C for "Sigma" makes for problems in decoding back to Greek, especially since it is the only letter available for "Chi" (unless X is used, thus posing a problem for "Xi"). And occasionally someone uses P for "Rho," making problems for how to represent "Pi."