The R pops up for the same reason "no smorking" is a thing. That O sound can get a bit confusing depending upon what's near it and usual patterns. It tends to crop up when the O is a long vowel in the furigana. The L/R thing is everpresent.
I think that's a British influence. Rs in English words tend to get transcribed into katakana as long vowels to resemble British pronunciation, like parking → パーキング or art → アート. For a Japanese person who hasn't formally learned a romanization system but knows a decent amount of these English → Japanese word pairs, it seems pretty reasonable to try to reverse the process by turning long vowels into Rs when writing Japanese in Romaji.
I found this one especially humorous because of how ubiquitous the word otherwise is.
Yeah, that's true; seems like there would be plenty of nearby places to check.
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Remember that you can add furigana to your posts by writing ~{KANJI|FURIGANA}~ like:
~{漢字|かんじ}~ which comes out as:
{漢字|かんじ}
