Japanese native speaker here. I might be able to help.

Unable to reproduce bug (works for me).

What was fixed by @Glaisher is just a side issue. The point of this task was to prevent username creation in the form of e.g. ConflictingUserName~enwiki and I do not see this issue being addressed in [[m:Title blacklist]] yet. Reopening.

My goodness you're right. That needs fixing.

Or even just
.*~.*wiki
because I realized we've already had
.*(wiki(books|data|news|quote|source|species|versity|voyage).* <newaccountonly>

Ha, that was dumb. Corrected it. But the language part is going to be one heck of a long regex.

A vandal has been reported to have taken hold of a user name that ends with ~jawiki in an attempt to impersonate and take over a (sub-)account held by a jawiki admin and bureaucrat. (This issue has been mentioned in jawiki's Village Pump: [[w:ja:Wikipedia:井戸端/subj/統一ログインへの完全移行に伴い名前が変更される利用者への個別メッセージ]].)

Japanese blacklist has been merged (thanks to Glaisher) as logged at [[m:Title blacklist/Log/2015/03]].

Minor edit regarding Japanese to remove the literal translation of "Special:MergeAccount" in parentheses which I needlessly included in the translation at Meta, as it was already a localized pagename. Changed one of the verbs to its more polite conjugate.

A comment from a native Japanese speaker: Generally, the ideographic full stop "。" is the equivalent of a latin-script full stop and is the most common sentence separator. (Same goes for Chinese.)

@Nemo_bis I copyedited P398 (a.k.a. "finalized text" according to Keegan's post above) after it was posted, and observed it being reflected on the actual messages that were posted. I don't know if the script actually reads it from there now, though.

@Keegan Thanks. Okay, now I see that the same concern had been raised in Gerrit too. I've already started the discussion at [[:ja:MediaWiki talk:Titleblacklist]] and will keep an eye on so that the discussion will not dwindle on for too long. Other wikis should do the same.

So when will this actually get deployed in the projects? Japanese Wikipedia has a lot of <newaccountonly> entries to counter vandal sock puppets. Some of them are just downright vulgar words which I see no problem with being in the global blacklist, but some entries are very wide-catching and made sense locally but would easily cause problems if merged globally (e.g. .*igasih.* or .*[1１][5５][6６].*). I would like to let jawiki admins know about this so that they can sort it out.