How the Lobsters front page works

Summary

Lobsters is a computing-focused community centered around link aggregation and discussion.The code is open source, so I had a look at how the front page algorithm works.This is it:$$\textbf{hotness} = -1 \times (\text{base} + \text{order} \times \text{sign} + \text{age})$$ $$\text{hotness} \downarrow \implies \text{rank} \uparrow$$The page is sorted in ascending order by \( \textbf{hotness} \). The more negative the value of \( \textbf{hotness} \), the higher the story ranks.You can skip straight to the interactive front page to help get a feel for the front page dynamics.BaseThe \( \textbf{base} \) is added to the order term to incentivise certain types of posts, and influence the initial ranking. It is the sum of the hotness modifiers (a value between \( -10 \) and \( +10 \) of all the tags in that story).$$\textbf{base} = \sum_{t \in \text{tags}} \text{hotness\_mod}_t + \begin{cases} 0.25 & \text{if self-authored link} \\ 0 & \text{otherwise} \end{cases}$$Some tags (like culture or rant) have negative "hotness modifiers", which penalises their initial rank. Authors submitting their own content get a tiny boost, which is mildly surprising given the otherwise strict self-promo rules. The \( \textbf{base} \) has a modest effect on the hotness compared to \( \textbf{order} \) and \( \textbf{age} \).OrderThe value of \( \textbf{order} \) is derived from the engagement that a story gets.$$\textbf{order} = \log_{10}\left(\max\left(|\text{score} + 1| + \text{cpoints}, 1\right)\right)$$The progression of the order term is logarithmic—this means going from 0 to 100 votes increases the rank far more than going from 1000 to 1100 votes.The \( \textbf{cpoints} \) is added to the story score, which accounts for non-submitter comment upvotes (a comment upvote is worth half a story upvote). If the \( \textbf{base} \) is negative (as is the case for a freshly submitted rant), then this term is zeroed, making the comments effectively contribute nothing to the rank.$$ \text{comment\...