Ebuilds should be limited to <= 18 digit version numbers, otherwise there will be breakage. See rationale in bug 270108, especially bug 270108 comment #2.
Created attachment 201930 [details, diff] Proposed patch for ebuild-writing/file-format/text.xml
Any objections if I commit this myself?
Looks sane and noone else from team said anything against it for 4 months. So feel allowed to go ahead :]
Thanks scarabeus and halcy0n.