A basic rule of Stack Exchange is that people can edit your work here. The edit history allows readers to sort out who is actually responsible for which words, but even so we are sensitive to the possible appearance that people are putting words in your mouth. That is part of why you should get notified every time your one of your posts is edited.
You have the power to re-edit or to roll-back changes you don't like. If an edit war begins to develop, don't engage with the other user, just flag the post using a custom flag reason and explain your point of view. A moderator will try to sort things out.
Most of the edits other users make to my posts are improvements in my mind as well as theirs. In most of the exceptions they things they worked on really was a deficiency, I just don't like how they tried to fix it and I re-fix it to my own satisfaction.
It is that ability to re-intervene if I don't like what they have done that lets me remain unperturbed by the ability of other users to edit my posts. I hope that it will do the same for you in time.
Addressing specifically the matter of low rep users introducing edits: those edits are not applied until after a edit review proccess in which they are seen by no few than two users with un-reviewed editing privileges. In this case the first two user to review the edit approved it and it was applied. This took approximately 5 minutes in this case, though I have seen edits pending for hours in the past.
Low rep users whose edits are routinely turned down can lose the privilege of suggesting edits and reviewer can lose that privilege as well if
(1) they fail enough review audits or (2) (seems review audits are not enabled on Physics SE right now) they come to the moderators attention for bad reviews too often.
So, again, the correct action if you think a edit that was made to one of your posts was improper is to flag the post so that a moderator (or several) will look at the situation. Even if we don't take action that time it can lead to our seeing a pattern and practice that might eventually lead to action.
In this case I think the low-rep editor was genuinely trying to help clarify some murky bits in you text and the reviewers agreed.
Concerning these particular edits, I have to say that reasoning like "Current is the reason why it is heating, voltage is the cause." is suspect and often the cause of confusion. To truly understand any given case you have to look carefully at what is constant in the situation and what is subject to case-by-case variation.
Many supplies in the everyday world (batteries, line power, etc) are approximately fixed voltage supplies. In those case the current is a consequence of the voltage and resistance. The form V^2/R give the best intuition for how the inputs (voltage and resistance across the short) affect the heat produced. Notice how you can read directly that lower resistance causes more power and that higher supply voltage causes the power to grow quadratically.
Yes, the usual form IV is correct, but you lose the intuition about the actual situation on the ground by suggesting that the current is something you have control of directly rather than being something you have to adjust by effectively turning another dial. In other words this is to some degree a choice made to help engineer things, rather than a fundamental choice, but there is widespread expert agreement on the matter. Jerry's edit improved your post, and you hurt it's quality by putting it back.
There do exist good approximations to fixed-current supplies and in those cases the form I^2 R give the best intuition. These mostly show up in electronics and I'm weak enough in the subject to not try to provide an example off the cuff.