Well… it was kinda suggested in a different thread that this might be an interesting topic to discuss…
As I’m sure a lot of you have noticed, there are a bunch of words that have the same kunyomi, sort of similar meaning, but different kanji.
As a few examples 見る, 観る, 診る and their buddies all are related to looking, 痛む, 傷む, 悼む all have to do with damage or hurt and 聞く, 聴く, 訊く all have to do with listening or hearing.
I remember discussing this with a Japanese chat buddy and she dug up a link to this page (in Japanese). The section related to this particular phenomenon is (b)倭訓にて誦すれば字義混同す.
Basically. It explains that:
i.e. ancient Japan had a pretty small vocabulary and for that reason there were a lot of words that had the same kunyomi (or wakun as they call it here) but many different kanji. And as a result we wound up with these 同訓異字 (lit. same kun, different character).