As I posted on the dev list, I found myself typing for the Nth time that you can't just change the schema and then just keep going, you usually have to delete your current index and start over.
So I started looking for a link to point people to instead, it's silly of me to re-type this over and over. It only took me 10-20 repetitions to come to that conclusion...
Which caused me to look at the ref guide, particularly the reindexing.adoc. I'd like to edit it pretty heavily to slant it towards encouraging people to reindex rather than give them much hope they can get away without doing so.
There's a particularly interesting line in the doc about "you usually make changes in your schema for a reason" (paraphrasing) that got me to thinking. Until everything is reindexed those reasons won't be served anyway, even for something as "safe" as adding a field you search on. So you'll have to reindex anyway an overwhelming percentage of the time. I think it's better to set users up to be ready for that than give them false hope that they can get away without it.
I'll attach a PR with my preliminary edits momentarily for comment. I have to put it aside for a while and look at it again with fresh eyes, but I thought I'd garner some comments along the way about the general direction.
I did think about changing the title to "All hope abandon, ye who enter here that you can change your schema without reindexing"...