There are two questions here; Copyright and readability. I'll address them in that order.
Since these are fan-transcriptions, copyright is an issue, but not much of one. This is a site dedicated to discussion of sci-fi and as such, posting even very large chunks of text (short of entire book chapters and large sections of original scripts) is well within the scope of "fair use" under pretty much every definition. Note that as far as I am aware, there have been zero takedown requests for any quoted text anywhere on the network, ever. You're safe to post and if you go overboard, it's likely that a high-rep user or one of the moderation team will tell you well before it becomes a legal issue.
Ah, now here's the rub. Posting slabs of formatted text makes questions next to impossible to read, let alone answer. You should pick quotes sparingly to illustrate your main thesis rather than allowing the quote to stand as the actual question. The link you've provided is a perfect example of a question that could be good, but has been ruined by someone overdoing it with the quotes.
My suggestion would be that you should ruthlessly edit everything you write, then look at all the quotes to see if they're really necessary. If you have even the slightest doubt, cut it out and see if helps. There's no hard 'n' fast rule, but if a quote forms more than 50% of a question or more than 75% of an answer, then you've probably gone too far.