Comment 1 for bug 1008115

groff_char(7) seems to document some oddities around phi:

  "These glyphs are intended for technical use, not for real Greek; normally, the uppercase letters have upright shape, and the lowercase ones are slanted. There is a problem with the mapping of letter phi to Unicode. Prior to Unicode version 3.0, the difference between U+03C6, GREEK SMALL LETTER PHI, and U+03D5, GREEK PHI SYMBOL, was not clearly described; only the glyph shapes in the Unicode book could be used as a reference. Starting with Unicode 3.0, the reference glyphs have been exchanged and described verbally also: In mathematical context, U+03D5 is the stroked variant and U+03C6 the curly glyph. Unfortunately, most font vendors didn't update their fonts to this (incompatible) change in Unicode. At the time of this writing (January 2006), it is not clear yet whether the Adobe Glyph Names `phi' and `phi1' also change its meaning if used for mathematics, thus compatibility problems are likely to happen – being conservative, groff currently assumes that `phi' in a PostScript symbol font is the stroked version.

  In groff, symbol `\[*f]' always denotes the stroked version of phi, and `\[+f]' the curly variant."

It might be useful if somebody familiar with Greek could take this up directly with groff upstream, since it seems that the needs of mathematical Greek may conflict with those of real Greek? It certainly seems odd that the definitions in glyphuni.cpp and uniglyph.cpp aren't mirror images of each other.