At what temperature should I soak black tea?

Soak tea in cold water before brewing

I don't think the few minutes of soaking actually make any difference. it will pull a bit of stuff out of the leaves and make them wet, but what really matters is the hot water. It sounds like this is a way to get water at a lower temperature, similar to what you suggested in your proposed "protect tea from hot water" statement. This is good for green and white teas, and maybe oolong, indeed, but essentially unnecessary for most other teas.

You don't really want boiling water for tea all the time. Joe provided this temperature table in his comment. Some temperatures for common teas in descending order of temperature: maté, rooibos or herbs (98 ° C); black (195-205F / 91-96C); Oolong (195F / 91C); flowering (180F / 82C); white or green (175F / 80C). With some types of tea (black, maté, rooibos, herbal) it is almost boiling - when the water is poured in and transfers some heat to the cup, it is a few degrees below the boiling point. I don't need to worry too much.

For other types of tea (green or white tea), ideally you want to add some water with a lower temperature. If you have a way of getting water at around 80 ° C - for example, some kettles may turn off automatically at a lower temperature - then just do that. However, when it's easiest to make boiling water, and if you fill your cup a little less than 1/4 of the way with room temperature (20C) water and fill the rest of the way with boiling water, the result is about 80C , just right for green tea!