While still in WordPress and the post saved, the big first letter showed when I displayed the post. When I logged out and went to the page, there was no big first letter.
(Now- here’s more. Before clicking submit, I went to check the post and reloaded it. The large letter appeared. To check it again, I reloaded and the large letter disappeared. I reloaded two more times and it did not reappear again.)
Thank you all for your responses. I’m going to check out the polyfill.
At this point it seems to be Firefox. This doesn’t happen on Vivaldi (and therefore it probably won’t happen on Chrome) or IE. Fortunately, it’s a relatively simple page and I don’t think most people will see a need to reload it. It just kinda’ freaked me out a little bit