Posted by: John Hudson
Thank you for the thoughtful comments.
Regarding the spacing of the diacritic marks before capitals, I will review the current spacing, but if I do make it wider I will still not make it as wide as I think you would like. I'm wary of typographic norms that result from mechanical limitations of previous technologies, especially if they seem to me counter to chirographic logic. Often, I can check that logic against centuries of manuscript tradition, but in the case of uppercase Greek accents this is not very helpful since accents in manuscripts (an in some early printed editions) are found above capitals and after capitals as often as they are found before capitals.
I'm currently doing some sanity checks on my Greek spacing, since I opened up the lowercase spacing in the last beta and want to make sure that this didn't cause any knock-on effects in my kerning. So I'll review the capitals accent positioning at the same time.
I'll take a look at the kerning of spacing accents question, but I'm not thrilled about the idea, because it really goes counter to the Unicode and OpenType model. Effectively, it makes the spacing accents non-spacing, and using kerning for this is problematic because it affects subsequent glyphs (I believe TeX has a way around this, but not all apps are so clever).
Regarding the contextual substitution of the different beta forms: I've not done this because it seems to be a specifically French convention that not everyone will appreciate. Personally, I quite like the convention -- it gives a pleasing variety to the text --, but it is so uncommon in the editions published outside of the French tradition that it seems unwise to include in a font intended for universal use. [After the SBL Greek is shipped, I'd be happy to consider making a private build for you, implementing this convention.]
Regarding the default form of phi: U+03C6 is the normal encoding for the Greek letter phi, so the decision about which form to encode at that codepoint depends on the style of type. There are a couple of things informing my decision to make the straight phi the default form in the SBL Greek font. The first is that it contrasts with my intention in the upcoming italic font, which is to make the loopy form the default. There are relatively few ways, in a Byzantine cursive style, to stylistically differentiate upright and italic fonts -- in addition, of course, to the slant of the latter --, and employing, respecitvely, the straighter and more cursive variants of some letter is one way to do this. The other reason is that in both the manuscript and early print editions that inspired the SBL Greek design, the straight phi is fairly common. Of course, in those sources the two forms are alternated fairly freely and not, so far as I've been able to determine, according to any rule: sometimes the straight form is used, and sometimes the loopy form. The variation in, for instance, the printed books of the Stephani is such that I think it very likely that the sorts for both forms were put in the same compartment of the type case, and the compositor used whichever he happened to grab.
U+03D5 is a symbol character, and I've only made use of it in the mapping of the alternate (in this case loopy) phi because it provides a convenient and standard way to encode a variant phi if someone wanted access to this form in a non-OpenType savvy application. I would be just as happy to leave the variant unencoded.
Now, all that said, I'm aware that quite a lot of people seem to simply prefer the loopy form and never want to use the straight form. I'm interested in a straw poll of SBL font users: how many people are happy with the current default phi form? and how many would prefer the loopy form to be default? (bearing in mind my comments above regarding stylistic differentiation of upright and italic fonts).