Rules that keep a translation working

1 min

Placeholders survive verbatim. %{count}, %{slug}, %{path} -- same set as the English string, spelled exactly. A renamed placeholder isn't substituted and the reader sees %{cout} in the output.
Prompts keep their trailing space. A string ending ": " puts the cursor one space after the colon; drop the space and input sticks to it.
There is no plural system, on purpose. Write count phrases so one wording works for any number -- the way the Czech locale phrases around its three plural forms, or a neutral Posts: %{count} shape. Don't invent one:/many: variants; nothing reads them.
Some terms stay untranslated: repost, boost, reblog name three distinct mechanisms on three networks and are established loanwords; Markdown and RSS are names.
Use your language's own typography -- quotes („…", «…», “…”), dashes, spacing. The English text is the meaning, not the punctuation.
Multi-line messages may reflow. Match the content, not the line count.