These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Canon Sue: Seaton is this — his interests, abilities and values are all either those of Smith himself greatly exaggerated, or ideals Smith held. (Indeed, all four of the main "good" Earth-human characters are Sued versions of real people — Dorothy Vaneman of Smith's wife, and the Cranes of his friends Dr Carl Garby and Lee Garby, Carl's wife who helped Smith with the "romantic" aspects of the first book.)
Unlike the Mardonalians, and the villains generally in the series, the Kondalians are not Absolute Xenophobes, but willing to co-operate peacefully with other planets. That said, they are typically portrayed as a species of Proud Warrior Race Guys, with a strong whiff of Barsoom. They're very flawed good guys, and they do occasionally get called out on their warmongering by the human protagonists.
Harsher in Hindsight: The Federation's war against the Fenachrone. The latter are a bunch of malignantly expansionistRubber-Forehead Aliens planning to expand from their own single planet; Seaton and company object to their plans. So far, so good. Their reaction, however, is first to threaten and bully the Fenachrone with their own overwhelming might until they declare war on them in desperation, then — When as defenders, they hold the moral high ground — nuke their planet and launch a near-successful attempt to exterminate the refugees completely. While it's clear the Fenachrone are aggressive militarists and potentially genocidal themselves, they also aren't really a threat to the vastly superior technology and numbers of the good guys at this point, and indeed have to display a fair amount of Villainous Valor merely in order to survive the attempted genocide. Besides the questions of Disproportionate Retribution and general Values Dissonance, to modern audiences the whole affair also reads a lot like the Roosevelt administration's historical warmongering and bullying of Imperial Japan, which ultimately lead to Pearl Harbor, the Pacific War and Hiroshima.