It’s fine in regular quantities.
The main reason we’re told to keep it out of the compost is that it won’t break down as quickly as other organic matter or that worms don’t like it.
This is similar to egg shells in the way that eventually it will break down and it is bringing amazing nutrients to the end result but the contents might not all be ready at the same time.
Some options of how to compost citrus
– separate and create your own citrus compost pile, compost as normal – see instructions here.
– chop up into small pieces or blend and add to compost as normal
– compost in a trench system
– compost as normal and know that the citrus might just take a little longer
If you host a dinner party and use 15 lemons, I’d keep these separate and do a trench compost.