RE what characters are valid for IDs: I found a few resoureces: SVG 1.1 has this chunk, which defers to the XML spec: https://www.w3.org/TR/SVG11/struct.html#IDAttribute XML has some BNF expressions to define the grammar, which do seem to allow hyphens: https://www.w3.org/TR/REC-xml/#id HTML5 apparently allows any non-whitespace character: https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/id
Bug 1572208 Comment 3 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
RE what characters are valid for IDs: I found a few resources: SVG 1.1 has this chunk, which defers to the XML spec: https://www.w3.org/TR/SVG11/struct.html#IDAttribute XML has some BNF expressions to define the grammar, which do seem to allow hyphens: https://www.w3.org/TR/REC-xml/#id HTML5 apparently allows any non-whitespace character: https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/id