Reduplication

koaan, koankoaan, koaarn'koankoaan

Duples

You can repeat monosyllable A to get A'A, for some emphasis.

koankoaan (high)
ang'aang (red)
khuikhuy ((adj) opened. cf. khuy`khuy, meaning "to open")
khiuxkhiu (QQ; chewy)
lau-khokkhog, etc (Online Abbreviations)

Triplication

You can repeat a syllable A three times (A"A'A) to mean extremely A. Generally, the first syllable undergoes tone change to the rare rising tone (#6; see Tones of Taiwanese).

aarng'ang'aang (紅紅紅 ; x. aang - red etc )
jiirn'jinjiin (仁仁仁 ; x. jiin - firm & full )
koaarn'koankoaan (懸懸懸 ; x. koaan - tall etc )
loaan'loaxnloan (亂亂亂 ; x. loan - disorderly; chaotic )
kaao'kauxkau (厚厚厚 ; x. kau - thick etc )
zeerng'zexngzeng (靜靜靜 ; x. zeng quiet )
kiirm'kimkym (金金金 ; x. kym - golden) )
khuiie'khuikhuy (開開開 ; x. khuy - wide open )
thoor'thothoo (塗塗塗 ; x. thoo - in shambles & completely lost )
kaao'kaokaux (夠夠夠 ; x. kaux - sufficient (cf. kaokaux) )
siirn'sirnsixn (信信信 ; x. sixn - believing without doubt )
kof'kofkor (古古古 ; x. kor - ancient )
leerng'lefnglerng (冷冷冷 ; x. lerng - cold; cool )
seek'segsek (熟熟熟 ; x. sek - commonly seen; acquainted with )
took'togtok (獨獨獨 ; x. tok - alone )
siaap'siapsiab (澀澀澀 ; x. siab - bitter; astringent )
siip'sipsib (溼溼溼 ; x. sib - moist (cf. sipsib) )

Zhamkhør

http://www.edutech.org.tw/Composition.htm
niaxnia (is this reduplication?)