[BUG] Reddit links result in 403 when run in Github Actions

[yogan]

Describe the bug Checking locally works find, but running in Github Actions leads to a 403.

To Reproduce Example README.md:

Redditor [u/Boojum](https://old.reddit.com/user/Boojum) has crafted a nice 
[surprise input](https://old.reddit.com/r/adventofcode/comments/18firip/2023_day_10_an_alternate_input_to_visualize/).

Relevant output from run in GitHub Action:

🚫 2023/day-10-python/README.md, https://old.reddit.com/user/Boojum , 403, 24, null
🚫 2023/day-10-python/README.md, https://old.reddit.com/r/adventofcode/comments/18firip/2023_day_10_an_alternate_input_to_visualize/ , 403, 25, null

I thought it might have to do with old.reddit.com, but this rewrite rule in .linkspector.yml did not help:

replacementPatterns:
  - pattern: "https?://old.reddit.com"
    replacement: 'https://www.reddit.com'

I'm not sure how I can get more details (e.g. headers) to see what is different locally and in GitHub Actions. I'll gladly provide more details if I can get some hints on how to get them.