Official spelling for her real-life counterpart. (As a general rule, most, if not all, Umamusume have their "Latin letter" names spelled in the same way as their real-life counterparts; that's why it's Tokai Teio instead of Toukai Teiou.
A related character with a similar name (Matikanefukukitaru) has her chartag spelled as one word.
The English fanbase tends to spell it as two words.
Separating the name into two makes it easier to parse the name.
--
Whichever way it goes, we'll have to add a _(Umamusume) qualifier later to keep things consistent with most of the Uma girls (and a qualifier is necessary anyway to disambiguate them from their RL racehorse counterparts). Some of the other Uma girls also have missing qualifiers but we'll leave that for later.
Separated from the above because I want to keep my personal opinions and arguments separate from the OP:
My preference is to use Matikanetannhauser because it's more consistent (agreeing with the official spellings and Matikanefukukitaru's chartag).
"Fandom" wikis have a reputation for being notoriously inaccurate (a sentiment shared by BrokenEagle98 in forum #189964). For Umamusume in general they have a tendency to use odd romanizations (disagreeing with official sources) and 'rote' ('wooden'-sounding) translations of character profiles. Some of them even contain outdated information like in the case of Air Groove (causing issues with English readers becoming bewildered whenever Air Groove acts chummy with the Trainer, like in post #4477470 and post #4635221. Because the Fandom wiki incorrectly states that she "bares (sic) an uncompromising hatred to men").
For Matikanetannhauser's name in particular, the Fandom Wiki is also inconsistent because they decided to follow official spelling for Matikanefukukitaru, but then went off the rails and come up with their own spelling for Matikane Tannhauser. So overall, what Fandom Wiki says shouldn't matter (at least for this particular case), and we can disregard their spelling. They can't even keep things consistent, including whether to follow official spelling or not.
The English fanbase seem to prefer using "Matikane Tannhauser", but overall I'd say it's an error propagated by the Fandom Wiki itself, as there aren't many English sources for Umamusume information.
I concede that it is important to take into consideration fanbase-preferred names, and that official names may not necessary be 'correct' for the purposes of our chartags, but here the fanbase-preferred names have a glaring inconsistency. It is like if you have two characters in the same copyright with the exact same surname ("Matikane-" kinda acts like one here, like the Airs and Mejiros), but the fanbase decides to go with different "romanization schemes" for both, because a fanwiki decided to spell both in different ways and the "error propagated".
--
Some additional info/trivia (on why their official names are so long):
Show
Umamusume characters generally follow the spelling of their real-life racehorse counterparts.
The racehorse Matikanefukukitaru was originally supposed to be named "Machikane Fukukitaru" ('ch' instead of 't', and as two words with a space), but because of international rules for racehorse names limiting maximum name length to 18 letters (including spaces), they had to shorten it down to Matikanefukukitaru (exactly 18 letters).
Matikanetannhauser is also exactly 18 letters, and likely spelled this way for the exact same reason as Matikanefukukitaru.
Separated from the above because I want to keep my personal opinions and arguments separate from the OP:
My preference is to use Matikanetannhauser because it's more consistent (agreeing with the official spellings and Matikanefukukitaru's chartag).
"Fandom" wikis have a reputation for being notoriously inaccurate (a sentiment shared by BrokenEagle98 in forum #189964). For Umamusume in general they have a tendency to use odd romanizations (disagreeing with official sources) and 'rote' ('wooden'-sounding) translations of character profiles. Some of them even contain outdated information like in the case of Air Groove (causing issues with English readers becoming bewildered whenever Air Groove acts chummy with the Trainer, like in post #4477470 and post #4635221. Because the Fandom wiki incorrectly states that she "bares (sic) an uncompromising hatred to men").
For Makitanetannhauser's name in particular, the Fandom Wiki is also inconsistent because they decided to follow official spelling for Matikanefukukitaru, but then went off the rails and come up with their own spelling for Matikane Tannhauser. So overall, what Fandom Wiki says shouldn't matter (at least for this particular case), and we can disregard their spelling. They can't even keep things consistent, including whether to follow official spelling or not.
The English fanbase seem to prefer using "Makitane Tannhauser", but overall I'd say it's an error propagated by the Fandom Wiki itself, as there aren't many English sources for Umamusume information.
--
Some additional info/trivia (on why their official names are so long):
Show
Umamusume characters generally follow the spelling of their real-life racehorse counterparts.
The racehorse Matikanefukukitaru was originally supposed to be named "Machikane Fukukitaru" ('ch' instead of 't', and as two words with a space), but because of international rules for racehorse names limiting maximum name length to 18 letters (including spaces), they had to shorten it down to Matikanefukukitaru (exactly 18 letters).
Matikanetannhauser is also exactly 18 letters, and likely spelled this way for the exact same reason as Matikanefukukitaru.
Honestly I think it is pointless to follow it. (I also blame the guy who name his horse that).
Besides as I said in my comment earlier, fandom don't literally (don't need) follow that. Not only it is hard to remember, but people are much used in "Matikane Tannhauser" than the one used for the horse IRL. Might be better if the actual horse tag uses it than the umamusume instead.
Honestly I think it is pointless to follow it. (I also blame the guy who name his horse that).
Besides as I said in my comment earlier, fandom don't literally (don't need) follow that. Not only it is hard to remember, but people are much used in "Matikane Tannhauser" than the one used for the horse IRL. Might be better if the actual horse tag uses it than the umamusume instead.
In that case I think we should split "Matikanefukukitaru" into two to keep consistency.
It looks like two words does have some official usage, because it is clearly that way on the anime website (inconsistent with the game website). I noticed one of the commenters on the Fandom Wiki page mentioned the association sets a limit of 18 characters. If that's true and includes spaces, it would explain the odd formatting in both cases.
Honestly I prefer the name used the most, and consistently used. Although I feel the one word name looks ugly. But eh, if the consensus leaning towards one name, I won't oppose it.
Honestly I prefer the name used the most, and consistently used. Although I feel the one word name looks ugly. But eh, if the consensus leaning towards one name, I won't oppose it.
I think that might another case. Besides "matikane tannhauser" had being consistently used that it sounds better than the "official" one.
