Affect vs impact

You can make up your own mind, but it's a fact that sticklers can object to the use of "impact" as a verb. To quote the usage note at American Heritage Dictionary:

Regarding the verb use of "impact" as a verb

The verb is a different matter. Many people dislike it because they assume it was converted from the noun in the manner of voguish and bureaucratic words like dialogue and interface, but in fact impact was a verb long before it was a noun—the verb dates from the early 1600s, the noun from the late 1700s. Most of the Panelists still disapprove of the intransitive use of the verb meaning "to have an effect": in our 2015 survey, 78 percent of the Panel (down only slightly from 85 percent in 2001) rejected These policies are impacting on our ability to achieve success. The transitive version was once as vilified, but is gradually becoming more acceptable: in 2015, only 50 percent (down from 80 percent in 2001) rejected The court ruling will impact the education of minority students, and only 39 percent (down from 66 percent in 2001) found the literal sense unacceptable in the sentence Thousands of meteors have impacted the lunar surface. Although resistance to the transitive senses is waning, the intransitive use is still strongly disliked and is best avoided. See Usage Notes at contact, impactful.
American Heritage Dictionary

So as you can see, approval of this use is quite all over the place and fickle over time periods.

Of particular note is this line:

In 2015, only 50 percent (down from 80 percent in 2001) rejected "The court ruling will impact the education of minority students."

A drop of 30% rejection in a matter of 14 years is quite remarkable in my opinion.

That isn't to say you should avoid its use, just keep in mind that there are plenty of people who disapprove of its use. There's no absolute reason why you should avoid triggering someone's disapproval.

Also, personally, "affect" and "effect" seem quite clear to me (if we disregard that "affect" can be a noun and "effect" can be a verb) - hmm, actually I take that back, haha. I have much bigger problems with other areas of word meanings.

There always seem to be different, often unrelated points being made when it comes to the word impact:

1. That it should not be used to mean "affect" or "an effect" because it means to forcefully come into contact with / strike something.
2. That it cannot be used as a verb because it was traditionally a noun.

While #2 is along the lines of argumentation that a lot of people seem to be immersed in, it's not the actual issue with the word (i.e., the process of making nouns into verbs has always happened and this word has undergone that process as well quite a long time ago); #1 is.

And even regarding that, people who claim that it cannot be used figuratively are probably being a little too conservative/traditionalist, seeing as words taking on figurative meanings is also a common and natural process in language. Even this is not the problem, however.

The main problem lies with people who use the words impact and affect (as a verb) or effect (as a noun) interchangeably. They mean different things. Affect simply means to have an effect or influence on; i.e., to cause something to change in some way. Impact, on the other hand, means to collide with or crash into something or to pack something in firmly when used literally.

Now, this can be extended to its figurative meaning, which can be used to mean "to affect something in a shocking, violent way" (when used as a verb) or "the shocking, violent effect of something on something else" (when used as a noun).

That is, affect means to have any kind of effect on something, while impact means to have a strong, often violent effect on something. Here is an example that should make it clear: let's say that I had a car accident.

• Our car was impacted in the accident, destroying it completely and resulting in broken legs for me. (Literal sense)
• After the accident, my life was impacted since I couldn't walk for 6 months. (Figurative sense)

As you can see, there's nothing wrong with either of these usages. Since losing your ability to walk is incredibly disruptive/painful, it would be safe to say the accident had an impact on your life.

The problem, of course, is when people use impact for any and every thing that wouldn't necessarily have been affected violently/shockingly. It was a trend that started in the business world, as with many things, to hyperbolize usage in order to make their statements "stand out". This is why such misuse is still within the realm of jargon. This is the problem most people have with the word.

What's more, there is another class of people who promote the use of impact over affect/effect simply because many people confuse the latter two words. This is not only poor advice, since it encourages people to avoid learning about the difference rather than teaching them it, but it also opened the Pandora's box we are dealing with today.

The problem with such use becomes especially evident in negative constructions. Your proposed example is a good one to illustrate the point:

Certain type checks allow reordering without impacting semantics.

Saying "without impacting semantics" means that "reordering" would not have a shocking/violent effect on "semantics". The problem with this, of course, is that it implies that it could still have a not-so-shocking effect on them, so you now have an unclear sentence. This is not to mention that, judging from the context, "reordering" would never have a shocking/violent effect on "semantics", so it would be incorrect usage even in the positive sense.

This is why, except in specific cases where an effect is incredible, shocking, or violent, the word impact should be avoided. You want affect when using the verb and effect when using the noun.