This issue is common to all RTL scripts.

For support of bidirectional text in plain text, the Unicode Standard provides a number of formatting characters, which include RLI, LRI, PDI and FSI. See an explanation of how these work.

Note that the Unicode Standard recommends the use of RLI/LRI...PDI rather than the former RLE/LRE...PDF, because the newer code points directionally isolate the text they surround from that around it. This is important for producing bidirectional text.

Although markup should be used most of the time in HTML pages, there are parts of an HTML document that don't support markup, such as the title element and title, alt, and other attributes. These characters can be necessary for managing inline runs of such text.

The Gap:

The RLI, LRI, FSI, PDI characters still don't produce the necessary behaviour in all major web browser engines.

Gecko and Blink support these characters. Webkit doesn't.

Spec status:

This is an issue related to Unicode support, rather than W3C specs.

html mentions that text content may contain these characters.

Tests & results:

i18n test suite, Isolating formatting characters

Action taken:

Webkit (2014)

Outcomes:

WebKit now supports the required behaviour for these formatting characters. This means that they can be used interoperably on all major web browsers.

Priority

These characters control fundamental behaviours for support of RTL scripts so priority is set as Basic.