Paragraph posting isn’t common in most walk up or public RP mostly out of consideration for others. There’s lots of conversations going on and dropping several paragraphs of text can make an already difficult time even more difficult. Even in guilds, when dealing with large group conversations/events, waiting for four or five other people to drop paragraphs means you can be sitting for long stretches while things drag out.
However, once you find yourself having a one to three person conversation, it’s rare to find anyone who doesn’t post at least one and a half paragraphs at a time. Usually much more.
With that understanding, I think pretty much any RP guild would suit your needs. Check out the Horde Guild Directory here, and take a moment to check out shamelessly plug for my own guild, Firebrand Enterprises.
And you shouldn’t go to Trade in search of RP contacts, unfortunately. You’ll have more luck hanging around Silvermoon City, the Valley of Honor in Orgrimmar, or the taverns in Stormwind. Browsing the forums/Discord channels/Tumblr in order to keep updated about organizations and events can also help.