Ilena=Ilene=Irene
(in translation of Japanese to English, R and L are interchangable. There's no L in Japanese. Though, this is only my limited understanding of someone who knows nothing about Japanese, Katatonic and all this language stuff, lol)
Rigardo vs Rigaldo
Galk vs Gark
Ilena-Ilene vs Irene
Renee-Rene-Rune vs Lune
..and surely more..
(there's also, Easley vs Isley, merely different spellings seen used, and other-more examples too of different spellings)
(Raftela vs Rafutela or something like this, meh)
(The Holy City: Rabona vs Labona)
(Eastern Land: Sutare: manga vs Sutafu: anime)
(Rubel vs Louvre)
(Rimuto vs Limt)
I think Ilena is suppose to be her correct name (and it does sound more like her too hehe), but I first heard Irene, so that's the name I use, and it is useful to use too, due to Elena (the only friend Clare initially had as a Claymore) vs Ilena, lol. So, I use Irene as it is unique and easily distinguishable from Elena.
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now.... if only we didn't still have to content with... (these *ARE* different characters)
Katea and Kate
Luciela and Lucia and Lutecia (3 similar names, argh)
Clare and Clarice
Rafaela and Raftela
Ilena (Irene-Ilene) and Elena
Miria and Miata
..and probably some more, I'm forgetting...
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(Mucha: The Southern Land vs Musha: Priscilla's home town in the Southern Land)
(Rabona-Labona: The Holy City in the Central Land vs Robano-Rabano-whatever-it-is / Toulouse: The Central Land. Obviously I use Toulouse to avoid the confusion with the Holy City, lol)
(Towns: Doga: Raki's Home town in South or West vs Dabi: town in North)