This third bug was not due to Debian patches. And in fact the two Debian patch cases in the article were included to make the point that they can now catch issues caused by distribution patches, not to claim that most of the issues they find are caused in this way. Assuming on the basis of an article written to make a wholly different point that because 2/3 were the result of distribution patches that this must be a huge problem in general for Linux software development just shows your bias on this issue.
I like and use Arch Linux on my desktops. But I'd defend the choice by Debian to patch. Most of Debian's changes are intended to improve support for certain setups or introduce bug or security fixes that upstream hasn't backported. These are both good things. Furthermore, problems that are created tend to be caught while they're still in unstable or sid: if I'm not mistaken that's exactly what happened in these cases, which is the process working as intended. (Mozilla is certainly free to disregard bug reports from Debian users if they feel that Debian's patching process is simply causing too many problems.)
This is misleading and in fact not even strictly true. They link three bugs, not two: https://bugzilla.mozilla.org/show_bug.cgi?id=1633459
This third bug was not due to Debian patches. And in fact the two Debian patch cases in the article were included to make the point that they can now catch issues caused by distribution patches, not to claim that most of the issues they find are caused in this way. Assuming on the basis of an article written to make a wholly different point that because 2/3 were the result of distribution patches that this must be a huge problem in general for Linux software development just shows your bias on this issue.
I like and use Arch Linux on my desktops. But I'd defend the choice by Debian to patch. Most of Debian's changes are intended to improve support for certain setups or introduce bug or security fixes that upstream hasn't backported. These are both good things. Furthermore, problems that are created tend to be caught while they're still in unstable or sid: if I'm not mistaken that's exactly what happened in these cases, which is the process working as intended. (Mozilla is certainly free to disregard bug reports from Debian users if they feel that Debian's patching process is simply causing too many problems.)