Distinguish tip and message on missing start date validator rule

data/core.yaml

@@ -1896,9 +1896,9 @@ en:
         reference: "Multipolygon members must have an inner or outer role."
     missing_start_date:
       title: Missing Start Dates
-      feature:
-        message: "Find features that are missing a start date"
-      reference: "Every feature should have a start date to prevent it from appearing since the beginning of time. If you are not sure about the start date, you can add an approximate date or a date range using the EDTF date field."
+      tip: "Find features that are missing a start date"
+      message: "{feature} has no start date"
+      reference: "Every feature should have a start date to prevent it from appearing since the beginning of time. If you are unsure of the start date, you can add an approximate date or a date range using the EDTF date field."
     missing_tag:
       title: Missing Tags
       tip: "Find features that are missing descriptive tags"

modules/validations/missing_start_date.js

@@ -44,7 +44,7 @@ export function validationMissingStartDate(context) {
       severity: 'warning',
       message: (context) => {
         const entity = context.hasEntity(entityID);
-        return entity ? t.append('issues.missing_start_date.feature.message', {
+        return entity ? t.append('issues.missing_start_date.message', {
           feature: utilDisplayLabel(entity, context.graph())
         }) : '';
       },