I read this and a bunch of other forums, and I think the root of the issue is ulitmatly arguing two different viewpoints of what the role of stewards are the "rules" and regulations should be versus on-track racing.
A lot of people will say that when Vettel did come back on track, he did come back quite "competitively" with elbows out and did gain some kind of "advantage" in the recovery of his "mistake" whether he was in control or not; he started racing pretty fast, vesus ceding a place for messing up.
It cuts to the core of what is a racing? When a mistake is made, should the capitalization on the mistake have to be earned on the track or should penalty be also backed up by rules/regulations. I suppose the answer they say is sometimes one and sometimes other, and it's for the stewards to decide.
Unfortunately, the core of the issue is F1 racing specifically is so stepwise in results with so little passing; that any "penalty" either has zero effect, so when they do have an effect it ends up being a huge effect and the stewards are hamstrung in what penalties they can give out.
Then, most of the time with this same type of mistake, they don't have to investigate, because 99% of the time "no advantage" is gained, as the places are not at risk, but the one time it does is when it comes down to a decision that nobody is happy with.
If Lewis is faster, why couldn't lewis pass vettel easily at another spot and make it official. If Vettel is faster, why doesn't vettel pull away by 5sec. The sport is broken when there is so few opportunities to make a difference.