Only tangentially related, but I'm always fascinated that mailing lists are still a thing in 2025.
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Like any implementation, it comes with certain affordances which differ from other implementations.
Messages feel "heavy" for several reasons: sending one involves a lot of clicks (or keypresses); if you send a very high number you may be banned from your email provider, and unable to communicate with anyone.
Messages often arrive instantly, but can be delayed up to hours or days, so conversation round-trips are kept to a minimum.
Messages are all the same - there are no "lite messages" such as emoji reactions - so any message must contain enough content to justify being a full-fledged message, or it won't be sent at all. (Sometimes an "emoji reaction" is felt to be enough content to justify a full-fledged message, which is sent.)
Being off the web increases the barrier to entry, reducing the eternal september effect (ironically, Usenet is one of the least eternal-september-ish of the public discussion boards currently in existence).
Overall, the feel of the system tends to somewhat discourage quantity and encourage per-message quality.
Haven't you heard about the abomination which is Office365? They recently bolted emoji reactions onto email!