This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Planeocracy
Lachesis telling her friends that she'll have to flee her homeland with Sigurd's army. Since the only known gate into Jugdral is in Agusty, this means she'll be unable to return unless another gate is discovered in Silesia. The post is here. The threads with Lyle and Ran — her two closest friends — are especially heart-wrenching.
Lyle'sreaction to Lachesis's disappearance from the organization, particularly since this is the second time something like this has happened to him. To make matters worse, his thread with Virgil points out the Fridge Horror in the situation.