This tool searches a text block for what appears to be NANO/BANANO addresses and verifies them for typos and duplicates. It will sort them into lists but also generate a visual output and add links to the block explorer.
Just paste anything, it will automatically warn about mismatches.
The recognition engine can't be uber confident about the actual cause, but it will certainly detect addresses that don't meet the NANO specs (lowercase letters, checksum, allowed characters, length, prefixes).
This tool will also recognize and sort out duplicate addresses.