Greek Unicode duplicated vowels

=Duplicated vowel+oxia characters in Greek Unicode range=

The problem
When Greek spelling was reformed in the 1980s, every accent was dropped except the oxia (acute). But experiments in typography at that time (e.g., rendering the acute nearly erect, or in the shape of a triangle), combined with the orthographical reforms, gave the false impression that all previous accents had been discarded in favor of a new and different accent, the tonos. Hence double code points for the vowels with oxiai made their way into fonts and into pre-Unicode encodings that were eventually folded into Unicode (which had to deal with legacy code tables). This legacy is evident in Unicode, which designated two major blocks:
 * Greek and Coptic (0370-03FF), which encoded the characters required for modern Greek: the 24-letter alphabet, a couple of numerical symbols, and vowels with tonos and/or diaeresis in addition to Coptic and a few other symbols. (Coptic was later moved to its own block, but the original name Greek and Coptic was retained for backward compatibility)
 * Greek Extended (1F00-1FFF), which handled polytonic Greek (for both classical and katherevousa Greek), which handled precomposed vowels with accents, breathing marks, subscript iotas, etc.

The Unicode Consortium soon recognized that the duplicated vowels preserved a false distinction. They therefore established normalizing rules that dictated that the upper code point should always be converted to the lower. But it is common to run into the problem of acute vowels encoded in Greek Extended.

Affected characters
For some reason, perhaps because of an oversight, or perhaps because the editors thought that there was some essential difference between tonos and oxia (acute)--which there is not--sixteen characters in the Greek basic set were duplicated in Greek extended:

There is no semantic difference between, for example, &#x03AC; and &#x1F71; (both alpha-oxia), so in most cases you don't need to worry about this. Your Greek Keyboards (Unicode) will make a decision and input one or the other. A search engine should be able to find both from either input (just as they should be able to strip diacritics altogether from a search term, if desired).

The Unicode database dictates a rule for normalization that converts the higher code point to its corresponding lower code point.

Most Greek Fonts (Unicode) will display both versions identically. A notable exception is Adobe Garamond Premiere Pro and Adobe Minion Pro, which observes the false distinction introduced in the 1980s by setting the oxia in the Greek and Coptic block at almost a vertical angle, and in the Greek Extended block at a slanted, ca. 45-degree angle. This can cause a problem with software that (correctly) normalizes the higher points to the lower ones, producing an inconsistent appearance in accentuation.

Recommendations
Tools and input methods should use the Greek and Coptic versions (GREEK [CAPITAL|SMALL] LETTER [ALPHA|EPSILON|ETA|IOTA|OMICRON|UPSILON|OMEGA] WITH TONOS) for these character combinations. Fonts and search tools should continue to support both for the sake of legacy data.

The latest versions of Unicode (as of 2016) have now formally deprecated and removed the vowel+oxia combinations from the Greek extended range, leaving only the vowel+tonos from the basic Greek and Coptic range.