Tom,

I've not noticed a significant change in highlight tonality as a result of gold toning, I use Tetenal or Fotospeed, perhaps a different toner such as Nelson Gold may affect the highlights. As Ann says, I do a lot of split toning with selenium and gold, selenium first and that increases the contrast by darkening the lower values in the image, followed by gold which significantly affects the higher mid values and bright highlights. I usually tone the print in selenium for up to 2 hours, I've even tried it for 4 hours but got bored, followed by a wash and then another 2 hours or so in gold. These times are just a guide for I always pull the print when it's at the colour I want it. The reason for the long toning times is purely because I experimented with times and temperature many years ago and liked the results. The process takes practice to learn to recognise the right time to pull the print but it's fun and a good hi fi is essential. Once you learn to anticipate the split you can get some quite exquisite results with this combination. If you work on the basis that the selenium changes shadows first and gold affect highlights first you will soon learn to anticipate. Don't be afraid to experiment and use different strength selenium, I use 1 to 4, 1 to 9 or 1 to 15 sometimes at very high temperatures. Gold is not diluted. I never tone by time as is sometimes suggested simply because of how the toners affect shadows and highlights. How can you have a standard time for prints of widely differing tonality.
Experiment and enjoy.