FYI in case I’m not the only one who didn’t grok the different effect between “delete” and “complete forever” in Todoist when applied to a recurring task providing data to a Beeminder goal:
DELETE a recurring task also deletes ALL the previous data in your goal that was provided to Beeminder by completing that task in the past. INSTANT derail if you’ve been completing that task for some time.
COMPLETE FOREVER a recurring task reports one final completion to the Beeminder goal, then the task disappears from Todoist BUT the prior data from it in your goal does NOT disappear!
Thanks to @shanaqui for telling me why I derailed from the Beeminder viewpoint so I could test various Todoist-Beeminder interactions to figure this out.