Steps to reproduce:

1. Create valid multilanguage content with TinyMCE disabled in user profile, for example:

<span lang="fi" class="multilang">Finnish content</span>
<span lang="en" class="multilang">English content</span>

2. Verify that the filter works correctly in both languages.
3. Switch back to TinyMCE editor in your profile settings.
4. Open multilanguage content in editor, and save.
5. Now the order of attributes is as follows:

<span class="multilang" lang="fi">Finnish content</span>
<span class="multilang" lang="en">English content</span>

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This breaks the multilang filter, and Moodle displays the content of both languages. The strange thing is that this bug can be reproduced in Firefox 12 & 12 (Win & Linux), but not in Chromium 18 (Linux). Somehow, in Chromium, the order of attributes does not change. We didn't test more browsers yet.

Regardless of how the order of attributes gets rearranged, I think the multilang filter should be able to detect multilanguage content in both cases, since the order of attributes should not matter in XHTML.

So as a fix I propose that both "<span class="multilang" lang="fi">Finnish content</span>" and "<span lang="fi" class="multilang">Finnish content</span>" should be valid ways to mark multilanguage content. Is this feasible?

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This affects a huge number of our courses, and probably all Moodle installations using multilang content. For example, when teacher tweaks quiz settings, the quiz description's multilanguage content stops working properly.