As stated, GitHub previews of Section Marks give out an error:
Sorry, this file is invalid so it cannot be displayed.
This could be due to the changes proposed by the W3C Candidate Recommendation for SVG2 (published on September 15, 2016):
W3C publishes a Candidate Recommendation to indicate that the document is believed to be stable and to encourage implementation by the developer community. This Candidate Recommendation is expected to advance to Proposed Recommendation no earlier than 15 July 2017, but we encourage early review, and requests for normative changes after 15 November 2016 may be deferred to SVG 3.
However, I couldn't find any evidence that supports GitHub had deprecated support for SVG version 1.1 (which is the current format of the files).
Oddly enough, other drawings could be previewed (even though they are also SVGv1.1).
luzpaz
commented
6 years ago
As stated, GitHub previews of Section Marks give out an error:
This could be due to the changes proposed by the W3C Candidate Recommendation for SVG2 (published on September 15, 2016):
However, I couldn't find any evidence that supports GitHub had deprecated support for SVG version 1.1 (which is the current format of the files).
Oddly enough, other drawings could be previewed (even though they are also SVGv1.1).