Recommended user ID column names to use
Community wiki answer:

I think naming the column as fieldtype_fielddescription, i.e. user_id_additional_info, is more safe.

For example, not user_subscribed_to_id = the user ID that was subscribed to, but user_id_subscribed_to.

It allows, for example, to select the fields packet from information_schema if needed, using a simple LIKE 'user_id_*' pattern.