Hi Andreas

Thanks for bringing this up and this seems indeed to be suboptimal.

> I wonder if Bitcoin Core would be willing to extend the BIP37 matching
> rules such that data elements in the witness are also matched against?

Bitcoin Core is not an identity that can be „willing to extend“ (or reject) a feature.
Someone needs to come up with a proposal (pull request).

Maybe an extension for BIP37 would make sense (*meh*).
Just inserting the witness data into the bloom filter seems to be an easy solution (CBloomFilter::IsRelevantAndUpdate())

/jonas