[masaegu]

Originally Posted by KyleGoetz

My question is about this sentence in particular: 誰もが話せばながい短いの差はあっても一篇の掌篇ぐら いになりそうな経験はもちあわせていようと思う。

I'm parsing the sentence as:
誰もが話せば = If everyone speaks,

This does not really mean that. You translated it as if 　「話せば」 were the verb for the subject 「誰でも」 in the mini-sentence. One needs to look at the whole sentence here.

It means "if (they were) willing to speak up, everyone (would have an experience that ~~~)".

「誰もが持ち合わせている」 is the core of the entire sentence.

ながい短いの差はあっても even if there's a difference between long and short
一篇の掌篇ぐらいになりそうな経験は an experience amounting to one short piece of writing

Precisely.

もちあわせていようと思う。 [??] is wanting/thinking/planning to have

This 「いよう」 means 「いるであろう」. An inference is being made here.

So I see 一篇の掌篇ぐらいになりそうな経験はもちあわせていよ うと思う as something like the author wants everyone to share his experience, which amounts to just about one short story in length. Right?

Yeah. The author surmises that everyone would have his own story to tell if it were about THAT day.

The first half confuses me even more. 誰もが話せばながい短いの差はあっても
If everyone speaks, even if there's a difference between "long" and "short"? I don't understand!

Is there an idiom in there I am missing?「誰もが話せば」の意味は何でしょうか。

You are not missing an idiom but are somehow not reading the sentence structure correctly. 「誰もが話せば」 is not an idiom. Pretend there is a comma after the 「が」 if it helps you.

Everyone has something. That something is an experience. If you can somehow get these people to tell their stories of their experiences, the stories would come in varied lengths.

Try reading the sentence with short pauses at the slashes below.

誰もが　/　話せばながい短いの差はあっても　/　一篇の掌篇ぐらいになりそうな経験　/　はもちあわせていようと思う。