Wow. That's pretty remarkable. Actually, Japanese combines three separate script types in one writing system: the semanto-phonetic kanji, two related but functionally distinct syllabaries (katakana and hiragana) and the alphabetic romaji.

Malay has also gone through six or seven distinct scripts belonging to three script types: three historically related syllabic alphabets/abugidas (old Kawi, a later Kawi-based Sumatran script, and early Javanese script), the central Malay bamboo script (and likely, though there is no direct physical evidence, its direct ancestor, a commercial script derived from early Gujarati script), the Arabic-derived Jawi abjad, and finally the Latin alphabet.

Javanese, Bugis and Makassarese also went the same route: first an Indic abugida, then a derivative of Arabic script, then the Latin alphabet, and Makassarese actually went through two distinct indigenous abugidas: Bugis-Makassarese script and another script often called "Old Makassarese" that despite the name was probably younger, being for the most part directly based on a variety nearly identical to the Sumatran bamboo script used by Malay.

Actually, Arabic script used to write Swahili underrepresented the sounds of the language even more than for other languages. In Swahili Arabic orthography, prenasalised consonants were only represented by the consonant itself and there was nothing in the spelling to hint at the nasal onset of the consonant. Similarly, consonants with a /w/ off-glide were written as the bare consonant alone – no hint of the /w/ sound. There were some other ambiguities in the script, though not as serious as these two.

I'd say Japanese uses three if you don't count romaji, four if you do. (I assume we're not counting Morse, Braille, semaphore, etc.) You might argue Chinese has four as well: trad. hanzi, simplified hanzi, pinyin (which is learned before hanzi), and zhuyin, though of course any one country only uses two of those.

Dozens of languages in Central Asia have been written with three or more scripts. Those that used Arabic or Mongolian and came under Soviet control switched to Roman and then to Cyrillic. Uyghur was written in Sogdian, the the Uyghur script (unless you want to count that as just a latter local form of Sogdian), occasionally Orkhon (Turkic "runes"), occasionally Syriac, then Arabic, Roman, and Cyrillic (local forms). That's what, seven?

Kurdish has been written in Arabic, Sorani, Armenian, Roman, Cyrillic. (Sorani looks like Arabic, but is functionally a full alphabet.)

Serbocroatian has been written in Croatian Cyrillic, Serbian Cyrillic, Glagolitic, Arabic, and the now-dominant Gaj's Latin.

Don't forget seal script, grass script etc.

I think Mongolian has had upwards of seven as well. Mongolian, Clear Script, Soyombo, Latin, Cyrillic, Chinese, Arabic etc.
Technically it's an extended Arabic alphabet, but I'll let this one slide.
There's a Croatian and Serbian Cyrillic? How much can they possibly differ?

See here: http://www.croatianhistory.net/etf/et04.html%20. I'm not sure how much is unique to this script, and how much is simply Old Cyrillic.

Calling it "Croatian", of course, makes you a bigot. As does not calling it Croatian.

I believe in Western typesetting we call them Ming, Sans-Serif (same as Hei), and "Regular" (which is kaiti.) I find any kind of serif font absolutely hideous, those damn serifs piss me off (although I can take them in Hebrew). Sans-serif/hei is definitely my favorite Chinese type-setting, I think it's just simplistic and absolutely gorgeous. I wish it were used more often though >.> Regular/kaiti is pretty, but somewhat tough to read. I think that they have use, in signs or advertisements and things like that, similar to all the different script typefaces for the Latin alphabet. In general, I think that sans-serif/hei should be used everywhere, it's my favorite

Outside Chinese fonts, I just want to give a shout out to Rashi script for Hebrew, it's just the most gorgeous way to write Hebrew! I'm not a fan of cursive Hebrew, it looks illegible and scribly to me, I write in a mixture of block and cursive Hebrew. Which is, honestly, the way I write the Latin alphabet as well

Does anyone know why you don't really see "fonts" in Arabic, online? I mean, it just all looks exactly the same (which, don't get me wrong, I think is beautiful no matter what). Arabic is, in my opinion, the best script for calligraphy. Chinese is nice, but grass script is really what's popular, and I grass script is an illegible mess of scribbles to me

Alright, no more script nerdgasming.

I've seen fonts for various calligraphic styles. But Arabic isn't linear. Much of it is written diagonally, and normal word processors can't handle that. (Yet!)

Manchu is a very nice script: it's beautiful, being originally written with brushstrokes. In the same vein, so is Mongolian. I like the Pahlavi script too.

Serifs in Latin are nice, when they're not overly used; they add a nice touch to otherwise simple blocky letters... Written Armenian or Georgian is absolutely gorgeous.

Sans-serifs in Chinese make the characters look ugly - a few serifs, here and there, make the characters less ugly and more readable.

The hiragana in Japanese are very nice, but they are somewhat square in that they have no descenders or ascenders, and one has to memorize a lot of syllables.

Well, I've memorized the hiragana, and I'm working on katakana. Now THOSE are square!

Tibetan can be beautiful when written correctly. If not, it's just a little too Indic for my liking.