I didn't know there was an official API! This explains why the data is so readily available in many sources and formats. That's very cool.

With a more straightforward approach, the tool can be reproduced with just a few queries in ClickHouse.

1. Create a table with styles by authors:

    CREATE TABLE hn_styles (name String, vec Array(UInt32)) ENGINE = MergeTree ORDER BY name

2. Calculate and insert style vectors (the insert takes 27 seconds):

    INSERT INTO hn_styles WITH 128 AS vec_size,
    cityHash64(arrayJoin(tokens(lower(decodeHTMLComponent(extractTextFromHTML(text)))))) % vec_size AS n,
    arrayMap((x, i) -> i = n, range(vec_size), range(vec_size)) AS arr
    SELECT by, sumForEach(arr) FROM hackernews_history GROUP BY by

3. Find nearest authors (the query takes ~50 ms):

    SELECT name FROM hn_styles ORDER BY cosineDistance(vec, (SELECT vec FROM hn_styles WHERE name = 'antirez')) LIMIT 25

        ┌─name────────────┬─────────────────dist─┐
     1. │ antirez         │                    0 │
     2. │ geertj          │ 0.009644324175144714 │
     3. │ mrighele        │ 0.009742538810774581 │
     4. │ LukaAl          │ 0.009787061201638525 │
     5. │ adrianratnapala │ 0.010093164015005152 │
     6. │ prmph           │ 0.010097599441156513 │
     7. │ teilo           │ 0.010187607877663263 │
     8. │ lukesandberg    │  0.01035981357655602 │
     9. │ joshuak         │ 0.010421492503861374 │
    10. │ sharikous       │  0.01043547391491162 │
    11. │ lll-o-lll       │  0.01051205287096002 │
    12. │ enriquto        │ 0.010534816136353875 │
    13. │ rileymat2       │ 0.010591026237771195 │
    14. │ afiori          │ 0.010655186410089112 │
    15. │ 314             │ 0.010768594792569197 │
    16. │ superice        │ 0.010842615688153812 │
    17. │ cm2187          │  0.01105111720031593 │
    18. │ jorgeleo        │ 0.011159407590845771 │
    19. │ einhverfr       │ 0.011296755160620009 │
    20. │ goodcanadian    │ 0.011316316959489647 │
    21. │ harperlee       │ 0.011317367800365297 │
    22. │ seren           │ 0.011390119122640763 │
    23. │ abnry           │ 0.011394133096140235 │
    24. │ PraetorianGourd │ 0.011508457949426343 │
    25. │ ufo             │ 0.011538721312575051 │
        └─────────────────┴──────────────────────┘