TrialTracker_MD said:

Vendor reputation tracking for vendor vetting: I maintain a personal spreadsheet with every order I've placed — date, vendor, batch number, Janoshik…

Same position here, arrived at the long way round. One addition: an unstated method makes a report close to uninterpretable. "99% pure" without the technique, the standard and the conditions is a claim, not a measurement.

One concrete data point for the thread. Keep the original post as written when you update it, and add the correction underneath. An edited-away mistake is invisible to the next person who makes it.

One thing that is still open after LabKate’s answer:

Whether a purity figure and a content figure can disagree without one of them being wrong?

Dr.PathRoch said:

Keep the original post as written when you update it, and add the correction underneath.

Pushing back on Dr.PathRoch here. Pushing back on the consensus forming here. Consistency is not the same as correctness, and a board that agrees with itself quickly is usually agreeing with the first person who sounded certain.

Correct me if the detail matters more than I have assumed.

Moderator note: good thread. Keeping it here rather than moving it, because the question is general enough to be useful.