diff --git a/README.md b/README.md
index c834a94..f3c788e 100644
--- a/README.md
+++ b/README.md
@@ -57,13 +57,23 @@ emoji's CLDR name and keywords in English, Korean and Japanese, and against
 ASCII aliases such as `->` and `<=`. `Ctrl+H` takes the syllable being
 composed as its query and composes on from it, converting a word as well as
 a syllable — 한자 gives 漢字, 대한민국 gives 大韓民國 — and `Esc` gives the
-syllable back. A reading is also the start of the longer words it begins,
-whose conversions follow its own, so 대한 answers 大寒 first and 大韓民國
-further down. A lone consonant is a reading too, and answers with the
-symbol table a Korean keyboard's 한자 key has always offered: ㅁ gives ※ ○
-△ ㈜, ㄴ the brackets 「」『』, ㄹ the units ℃ ㎏ ℓ, ㅇ the circled numbers
-①②③. Text already committed belongs to the application and cannot be
-converted.
+syllable back. A word is committed a syllable at a time, so the reading
+also reaches back into the text the application already holds, as far as
+the dictionary knows the whole of it: type 한자 and then `Ctrl+H` and the
+query is 한자, not 자, and picking 漢字 takes the 한 back. A reading is
+also the start of the longer words it begins, whose conversions follow
+its own, so 대한 answers 大寒 first and 大韓民國 further down. A lone
+consonant is a reading too, and answers with the symbol table a Korean
+keyboard's 한자 key has always offered: ㅁ gives ※ ○ △ ㈜, ㄴ the brackets
+「」『』, ㄹ the units ℃ ㎏ ℓ, ㅇ the circled numbers ①②③.
+
+Reaching back needs the application to hand over the text around its
+cursor and to take some of it away again. The Wayland input method, IBus
+and the GTK 3 module all can; XIM has no such request, so there the
+reading is what is still being composed and nothing else, and an IBus
+client that reads a key's effects only after the call returns is not
+asked for its text either, since a deletion could not be ordered before
+the commit.
 
 Dead keys and Compose sequences are composed by strans itself for the
 Wayland, XIM and IBus frontends, from `XCOMPOSEFILE` or the locale; the
@@ -71,12 +81,12 @@ GTK 3 module leaves them to GtkIMContextSimple.
 
 ## Preedit and candidates
 
-| Frontend | Preedit | Candidates |
-| --- | --- | --- |
-| Wayland input method | inline in the client | popup |
-| GTK 3 and IBus | inline in the client | popup |
-| XIM PreeditCallbacks | inline through XIM callbacks | popup |
-| XIM PreeditPosition, PreeditNothing | popup | popup |
+| Frontend | Preedit | Candidates | Reaches back |
+| --- | --- | --- | --- |
+| Wayland input method | inline in the client | popup | yes |
+| GTK 3 and IBus | inline in the client | popup | yes |
+| XIM PreeditCallbacks | inline through XIM callbacks | popup | no |
+| XIM PreeditPosition, PreeditNothing | popup | popup | no |
 
 On Wayland the popup is a surface the compositor places at the text cursor,
 flipping it above the line when there is no room below. Elsewhere it is an