When note editing support was added, it was omitted to strip internal
fields from edited notes and their history.
This was uncovered due to Mastodon inlining the like count as a "likes"
collection conflicting with our internal "likes" list causing validation
failures. In a spot check with likes/like_count it was not possible to
inject those internal fields into the local db via Update, but this
was not extensively tested for all fields and avenues.
Similarly address normalisation did not normalise addressing in the
object history, although this was never at risk of being exploitable.
The revision history of the Pleroma MR adding edit support reveals
recusrive stripping was intentionally avoided, since it will end up
removing e.g. emoji from outgoing activities. This appears to still
be true. However, all current internal fields ("pleroma_interal"
appears to be unused) contain data already publicised otherwise anyway.
In the interest of fixing a federation bug (and at worst potential data
injection) quickly outgoing stripping is left non-recursive for now.
Of course the ultimate fix here is to not mix remote and internal data
into the same map in the first place, but unfortunately having a single
map of all truth is a core assumption of *oma's AP doc processing.
Changing this is a masive undertaking and not suitable for providing
a short-term fix.