We’ve detecting more and more long names for highways, like I once reported here: http://www.openstreetmap.org/user/karussell/diary/26055
As discussed there the names are from official source but should we really include this in the name tag?
E.g. for navigation, do you think that ‘Please turn right into Москва — Малоярославец — Рославль до границы с Республикой Беларусь (на Бобруйск, Слуцк)’ makes sense 
?
I suspect this is a case of using a description rather than leaving the way un-named, which is what you should do with un-named ways.
However, I also don’t believe that the name tag carries any guarantee of being directly usable for voicing in a navigation program. For example, a road may have a name in more than one language in a country where maps are normally presented in both languages.
Really? Do you have a wiki link?
I do not understand this example. For this we have name:de, name:ru tags or what did you mean?
I’m not clear whether you are referring to the whether or not it is really a description, or the invention of names which are really descriptions
For the first, I don’t read Russian and Google Translate fails to translate it, so I’m making a guess based on it seeming to contain place names and is too long to be a name in its own right.
I thought it was sufficiently well known that name should not be used for descriptions that there was no need for the wiki to be explicit abut this. Even though you will get validation warnings for not naming a public road, that does not mean it is wrong, and you should not be filling the gap. In this case, there is a reference that could be used instead, once the name tag is omitted. http://wiki.openstreetmap.org/wiki/Proposed_features/Noname discusses possible ways to handle unnamed roads.
The convention for Japan is to give both the Kanji and Romaji (Latin alphabet) versions of place names. Although de facto mapping in Sri Lanka seems to being done in a minority language, English, it would appear that road name signs are actually given in up to three languages. As the rule is, in disputed areas, to use the name that actually appears on the sign, my view is that they should actually be mapped as a concatenation of all the languages used on the sign, in the order in which they appear.
The relevant section of the wiki re names vs descriptions is I believe http://wiki.openstreetmap.org/wiki/Names#Name_is_the_name_only.
Thanks @SomeoneElse! I’ve posted this to the tagging mailing list too to confirm this and see what we should do about it:
https://lists.openstreetmap.org/pipermail/tagging/2015-September/026641.html