For a very long time (ive not checked recently) slack used more memory that my IDE on a multimillion line c++ project. I used to have to shut down slack to compile on a machine with 128GB ram.
It definitely has improved. It was clear from the memory usage vs community size that they were doing something that scaled with community size. This is a guess, but something like loading every single user and their profile icon into memory.
At least in my case, I once caught Slack.exe on windows using 40GB of RAM. (My machine had 32GB, so you can imagine how well things were running.) The allocated space seemed to have mostly been zeroes since the Windows Kernel was able to compress a bunch of the pages to avoid running out, but it was putting so much strain on things that audio playback was dropping out.
