To piggy back on this, knowing the exact pressing of my CD [in my collection] is very important to me, but I’ve noticed the same usage as IvanDobsky. I do my best to try to add this info or clarify it where it exists (on top of adding scans of the matrix). I often think about how great it would be to get a field for this (https://tickets.metabrainz.org/browse/STYLE-781) and guidelines to help us standardize: where to begin/end, spacing, pressed chars (A01), bizarre chars (⟡), barcodes, mastering and mould source ID codes (SIDs).
Another curiosity of mine is similar but different mastering and mould codes, often called variants, and how to determine which should be grouped together in a release or separated into two releases. Discogs generally does quite well with this, however I’ve seen some questionably different variants on the same release before.