Defederation will result in an effective shadowban, just due to the way Lemmy is structured. If you yourself can’t find one of your own, though, that indicates it was probably removed, which is different from a shadowban.
Standard forum-system here, each community sets its own rules and moderation strictness, so best to read the sidebar before you participate. Some communities are extremely strict, others are extremely loose. Applies to whole Instances too.