Tying a user to a phone number does nothing but invade the privacy of most users, and slightly increase the costs for those who value their privacy.

Source: at https://smsprivacy.org/ I run an online service offering completely anonymous phone numbers for ~£3/mo. And note that you only need 1 month in order to get the account validated. Most places check the phone number once at account creation time and then never again.

It also has the effect of increasing the price of running 1000 bots to £3000/mo.

No, £3000 startup cost, not monthly cost.

Because having anonymity on public forums is important.

These days it seems like an illusion with respect to government oversight, and having a username is a simple way to anonymize yourself against your peers.

I'm all for it since it seems like it would reduce trolling.

That seems to me to pretty severely contravene reddit's basic philosophy.

They don't even require an e-mail address. A great thing about reddit if you ask me.

Metafilter had a great system. If you want to register an account, you pay $5 toward site maintenance. Presumably this would heavily discourage bots while still allowing folks to maintain alt accounts.

A lot of people would rather not give reddit their phone number.

Reddit's model has anonymity at it's very core. I follow a lot of things on the site and speak a lot about things about which if my parents or my family knew it would be embarassing. Not bad things, but simply things like /r/TIFU.

Too much signup friction, that would go against the status quo of growth = revenue.

sounds like a surefire way to get rid of most of their user base.

Reddit being a cesspool due to anonymity and its established userbase is its DNA. A service like you describe wouldn't be a bad idea, but it wouldn't be Reddit.

novelty accounts are a part of the culture