Learn German: Wir teilen diese verrückte Vorliebe.

The placeholder es is only used when the direct object of the verb is an entire following subordinate clause or an infinitive phrase. For example, if you said Wir lieben es, diese Vorliebe zu teilen (We love to share this preference), the es points to the infinitive phrase. Here, the object is just a standard noun phrase (diese verrückte Vorliebe), so no placeholder is required.

Why is the adjective ending -e in verrückte instead of -en?

Vorliebe is a feminine noun acting as the direct object, so it is in the accusative case. The word diese takes the primary case ending and acts as a definite article, which triggers weak adjective declension. The weak ending for the feminine accusative case is simply -e.

Can teilen be used to share abstract things like a preference, or is it just for physical objects?

Just like in English, teilen works perfectly for both. You can share physical things like a pizza (eine Pizza teilen), but also abstract concepts like an opinion (eine Meinung teilen) or a preference (eine Vorliebe teilen).

If I want to mention what this preference is for, what preposition should I use with Vorliebe?