I've gone ahead and "updated" the rules to how they read in Necturna's dex entry thread. It seems they were ripped from Tomohawk's dex entry thread, causing the CAPITAL LETTERS debacle. They don't have to be in CAPS for Black and White.
Things I think we should avoid:
Mentions of a life cycle - Some entries talk about Mollux hatching, but I think that this is just going to cause problems if the community votes to give Mollux pre-evos.
Mentions of other Pokémon - Okay, I was guilty of this with my entries for Necturna, but there's a point to this. It's extremely rare for two Pokémon to have enough of a relationship to mention each other in Pokédex entries. That's just a fact. (I'm also pretty sure we've gone past the Delibird bashing, so lol.)
Convoluted descriptions - Really, the majority of Pokédex entries are pretty simple. I find that a lot of entries overuse adjectives. I feel that people get really in-depth into the entries in an attempt to be "different". However, "different" and "creative" are two different things. I'm going to respond to this in particular:
I look at some entries simply talking about how it glows brightly exactly like a lava lamp does or how it hunts exactly like a cone snail does, and it's hard to get excited about those because they don't really give any information that wasn't already expected.
On the contrary, I know that people get tired of people stating "the obvious" and being "different" sticks out, but "standard" entries definitely have merit. If an entry is not really "different" but is still well-written and generally reads like a Pokédex entry, then that can still be a great, even creative, entry.
(BTW the double meaning usage of Mantle is cute but it triggers my science alarm because nothing lives as deep as the mantle.)
Likes:
Birkal's Black entry is fun, but I do have somewhat of a problem with it. In general, I find that a lot of entries kind of assume that Mollux lives somewhere without outright stating it. I happen to have an image of it living underwater due to those cone snail videos that have been floating around.
On that note, Jirachi6's entries are cool because they give a good picture of where Mollux might actually live. I would probably just reduce "almost impossible" to "difficult", though.
SubwayJ uses the "cliché" approach, with Black describing a ludicrously hard shell and White spouting the "no one's seen inside" business. Game Freak recycles these themes occasionally for a reason. Simple, effective.
Sound's oil spill idea is awesome. I think the first sentence actually detracts from it and should be removed altogether.
---
Updated my entries:
Species: Lava Lamp Pokémon
Black: It illuminates its shell to attract prey. It stings its victims with a powerful poison, then swallows them whole.
White: There are two liquids inside Mollux's shell. One provides sustenance, while the other is a deadly poison.