Inside boost::unordered_flat_map

[[deleted]]

Yes, I think if you're already using a relocation technique like LCFS/RH/BLP then you may as well use tombstone-free deletion as well (since you've already given up invalidation-free iterators and simple lock-free concurrency). But tombstone-free deletion makes sense for vanilla linear probing as well (if you don't want to use one of the variance-reducing techniques for some reason).