Need clarification about U+0F0E TIBETAN MARK NYIS SHAD

[lianghai]

Just a heads-up for now:

Unicode folks have recently received a report from @dscorbett (https://www.unicode.org/L2/L2019/19124-pubrev.html), asking for clarification about the expected look and behavior of this character:

Date/Time: Tue Apr 2 10:41:35 CDT 2019
Name: David Corbett
Report Type: Error Report
Opt Subject: Confusion regarding the glyph of U+0F0E TIBETAN MARK NYIS SHAD

Regarding Tibetan punctuation, chapter 13 says “Because some writers use the
double shay with a different spacing than would be obtained by coding two
adjacent occurrences of U+0F0D, the double shay has been coded at U+0F0E
with the intent that it would have a larger spacing between component shays
than if two shays were simply written together. However, most writers do not
use an unusual spacing between the double shay, so the application should
allow the user to write two U+0F0D codes one after the other. Additionally,
font designers will have to decide whether to implement these shays with a
larger than normal gap.”

I’ve downloaded a bunch of Tibetan fonts and most of them display U+0F0E as
slightly narrower than two U+0F0Ds. Many make them the same width. A few of
the Qomolangma fonts make U+0F0E slightly wider. The code chart glyph for
U+0F0E consists of two shays so close together there is barely any space
between them. If the standard is correct, the code chart glyph is
misleading, if not wrong, and should have more space between the shays. If
the majority of my test’s fonts are correct, chapter 13 should not imply
their spacing is wrong.

As the TLReq draft currently holds some of the best information (see ISSUE 2) about this character, I figured I should give a heads-up here and expect contributions to our investigation from W3C-side experts!

The Script Ad Hoc Group will be looking into this issue.

Currently my personal impression is:

This character was encoded as a magical character to allow that magic of spacing out two shays to happen at where this character is used. But it’s become clear that this character is not very helpful for that matter, because it relies on specialized typesetting environments, and also, the first shay for such spacing out situations is often absorbed by the preceding letter’s vertical stroke (and this character with two shays probably cannot be used).