There are quite a few titles which have appeared on the HN front page more than once. I've got an archive that's current as of a week or so back, and it shows 1,734 repeated titles.

The following 39 titles have appeared on the front page 5+ times, based on an exact text match, excepting a year indicator in parentheses, e.g., "(2023)". Note that the apostrophe glyph differs in the 2nd & 3rd entries for Peter Roberts AMAs:

     1   10 OpenSSL Security Advisory
     2    7 I'm Peter Roberts, immigration attorney who does work for YC and startups. AMA
     3    7 I’m Peter Roberts, immigration attorney who does work for YC and startups. AMA
     4    7 Richard Feynman and The Connection Machine
     5    7 The Architecture of Open Source Applications
     6    7 The TTY demystified
     7    7 Why GNU grep is fast
     8    7 You and Your Research
     9    6 Bit Twiddling Hacks
    10    6 Dictionary of Algorithms and Data Structures
    11    6 How to be a Programmer: A Short, Comprehensive, and Personal Summary
    12    6 The Bipolar Lisp Programmer
    13    6 Why Lisp?
    14    5 A Primer on Bézier Curves
    15    5 A regular expression to check for prime numbers
    16    5 Advanced programming languages
    17    5 Akin's Laws of Spacecraft Design
    18    5 Ask HN: Idea Sunday
    19    5 Ask HN: What are you working on?
    20    5 Beej's Guide to Network Programming
    21    5 DNA seen through the eyes of a coder
    22    5 Data Structure Visualizations
    23    5 How Software Companies Die
    24    5 How to Read Mathematics
    25    5 How to Write a Spelling Corrector
    26    5 Learning Advanced JavaScript
    27    5 Notation as a Tool of Thought
    28    5 Statistical Data Mining Tutorials
    29    5 Structure and Interpretation of Classical Mechanics
    30    5 Teach Yourself Programming in Ten Years
    31    5 Ten Rules for Web Startups
    32    5 Terms of Service; Didn't Read
    33    5 The Book of Shaders
    34    5 The Scientist and Engineer's Guide to Digital Signal Processing
    35    5 The Tao of Programming
    36    5 The case of the 500-mile email
    37    5 Who Can Name the Bigger Number?
    38    5 Why Lisp macros are cool, a Perl perspective
    39    5 You can't tell people anything

A further 67 titles appear 4 times each, 259 appear 3x, and 2,120 appear twice.

("Front page" here means the archived HN front pages under the "past" link at the top of the page here.)

Data through 2023-06-21.

I could run the analysis based on the URL rather than title, but that would require parsing the raw HTML which I've yet to do.