Well, I broke down and wrote a Lang-8 entry asking people to write the first verb that comes to mind when they see 「反る」, and I got ton of useful information from the responses.
First, the statistics: out of 15 responses, 13 people said that 「そる」 was the first verb that they thought of, while only 2 people thought of the 「かえる」 reading.
Some of the responses were extraordinarily interesting. I will copy-paste some of them here for your viewing pleasure, along with my poor attempt at a translation:
[quote]「かえる」という読みも小説か何かで見たような気もしますが、「そる」としか読まないと思います。
I feel like I've seen the 「かえる」 reading in books before, but I only read it as 「そる」。
[/quote]
[quote]「もどる(戻る)」とか「かえる(帰る)」という動詞が頭に浮かびました。
Verbs like 「もどる」 and 「かえる」 popped into my head.[/quote]
[quote]
「反る」の読み方は「そる」なのですが、これを読んで、まず頭に浮かぶ動詞は、「そりかえる」とか、「のけぞる」とかですね。
The way that I read 「反る」 is 「そる」, but when I read it the first verbs I thought of were ones like 「そりかえる」 and 「のけぞる」.[/quote]
[quote]「(かえる)? いや、(そる)だよなー、やっぱり・・・」とおもいました。
I thought, "「かえる」? Nah, really it's 「そる」 after all, isn't it..."[/quote]
[quote]なぜか、頭にパット「戻る。」のイメージが浮かび上がってきました。辞書をみると「もどる。」とは読みませんね。基本的な私の漢字の知識も疑わしいものです。
For some reason, the image of 「戻る」 flashed instantly into my mind. Though when I looked in the dictionary, 「もどる」 isn't listed there. It seems that even my basic knowledge of kanji can't be trusted.
[/quote]
[quote]どうしても2通りの読みが想起される。「そる」と「かえる」。 あと頻度で言うと「反る」は「そる」と読む場合(人)が多いと思う。「かえる」という読みは、今の日常語ではまれにしか出会わないと思う。
Ultimately, two ways to read it come to mind: 「そる」 and 「かえる」. Still, many people are going to read 「反る」 as 「そる」. As for the 「かえる」 reading, it's seldom encountered in everyday modern Japanese.[/quote]
As you can see, the results are for the most part as expected, with the bulk of people associating 「反る」 with the 「そる」 reading. However, I was a little surprised to see that there were several people who still associate the word with ideas of "returning." I should note that the woman who quickly thought of 「戻る」 is elderly, which makes me wonder if members of her generation would be more likely to make this "return" association for the word 「反る」. It's certainly an intriguing possibility.
Finally, I'd like to share this section of text extracted from a kotobank.jp page that someone on Lang-8 showed me:
[code]大辞林 第三版の解説
[表記]かえる ( 返 ・反▽ ・帰 ・孵▼ )
「返る」は“物がもとに戻る。もとの状態に戻る”の意。「貸した本が返る」「童心に返る」「我に返る」「あきれ返る」
「反る」は“向きが逆になる”の意。「返る」とも書く。「葉が裏に反る」「軍配が反る」
「帰る」は“もとの所にもどる”の意。「還る」とも書く。「家に帰る」「故国に帰る」
「孵る」は“卵がひなになる”の意。「卵が孵った」「ひなが孵る」[/code]
http://kotobank.jp/word/%E8%BF%94%E3%82%8B%E3%83%BB%E5%8F%8D%E3%82%8B
Here we have some fairly concrete evidence (Daijirin is a pretty authoritative source) of how to approach the 「かえる」 reading of 「反る」. As mentioned in a previous post, this reading is used for ideas of "turning over" or "flipping over," although as the explanation notes 「返る」 can also be used for this purpose. It would appear that which form to use for this meaning is at this time essentially a stylistic choice. Judging by the number of people who read 「反る」 as 「そる」, though, perhaps it is best to steer away from 「かえる」 readings of 「反る」 altogether, and instead use 「返る」. While the intended meaning can almost always be deduced from context, sometimes for the sake of clarity and ease of reading one choice can be slightly preferred over the other (just as in English writing).