I don't think so, somewhere else in this thread the developer of this job board says that his intention is to keep all listings forever, as this would prove that paid FOSS jobs exists in abundance. IMO a debatable approach.
No. I want to keep them around, sure, but of course they can be styled differently.
I don't know what makes everyone so upset at old listings. They are listed chronologically, there is an RSS feed to follow for fresh things. It's not like it's thousands of mixed jobs where you have to hunt for the recent postings? I definitely don't object to someone adding an archive/expiry functionality that does not completely delete old job listings. If you look at the referenced ticket on github, I created it.
Nobody is suggesting old jobs should be deleted from your database (I doubt any job listing website would do this). Just that the old jobs are too irrelevant to display by default as visitors are generally only interested in current vacancies.
Keeping the old jobs as a separate search option (eg "[ ] include historic items") de-clutters the primary purpose of the site. That matters when you consider that few people enjoy the process of job hunting so will quickly abandon any platform with a poor signal to noise ratio.
I think that's silly. There could have been hundreds of well-paid FOSS jobs in 2013. That doesn't matter at all if there are none in 2017. It doesn't even prove anyone was ever hired for that job, only that it was posted.
There's certainly analytical value in having every FOSS job you could have ever seen, but none for the end user.
https://news.ycombinator.com/item?id=13920594