Please have a look at http://bugzilla.novell.com/show_bug.cgi?id=274986 The reporter claims that "ft" and "rt" need more spacing. I found that these glyphs are spaced similary close in other fonts, e.g. in "Albany AMT", "Verdana", and "Segoe UI". And using the kerning in freetype 2.x makes "ft" and "rt" even closer. Therefore I wonder whether this is really a bug or whether this spacing is intentional.
In Sans Book "ft" has kerning -36, "rt" has no kerning. In Sans Bold there is not special kerning for either. These come from Bitstream Vera Sans and were not modified. Kerning mode in freetype 2 looks like a bug. https://bugzilla.novell.com/attachment.cgi?id=140508&action=view Although some might say this is fine since it makes "ft" look like a ligature and "rt" doesn't seem to be affected. When looking at kerning you have to consider the volume between the glyphs, not just the space between their ends. For example, look at the space between the stems of "ft" in comparison with the space with the right stem of 'a' or the stem of 'i'. Some fonts actually have a ligature for "ft". All the sans serif fonts I've seen have "ft" and "rt" in a similar manner. Closing as this is not a bug but a feature.
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