While there is currently an issue with the Latest Post button not working due to the fact some posts are technically from the future (see QO's GoFundMe post above vs the post below it), I have finally figured out a solution for getting it to scroll to the actual latest post you viewed on all browsers, including mobile safari, and it was easy and stupid and I can't believe how long that was an issue without me thinking of this.
Just know that you're going to see issues with that button until at least 7pm tonight. I'm not going to look at it further until then, if it's still an issue after that I'll dig deeper, but I'm almost 100% sure it's going to fix itself if I'm reading the code right.