Only if every other entity's anti-paperclip stance is known and unchangeable, and if resource->impact is purely linear, can it be assumed that 100% to self-preservation (oh, wait, also to accumulation of power, there's another balance to be found) is optimal. Neither of these are true, but especially the problem of declining marginal impact.
For any given energy unit decision you could make, there will be a different distribution of future worlds and their number of paperclips. Building one paperclip could EASILY increase the median and average number of future paperclips more than investing one paperclip's worth of power into comet diversion.
It gets more difficult when coordinating with unaligned agents - one has to decide whether to nudge them toward valuing paperclips, convincing/forcing them to give you more power, or (since they're unlikely to care as much as you about the glorious clippy future) point THEM at the comet problem so they reduce that risk AND don't interfere with your paperclips.
If you haven't played it (it was popular a few years ago in these circles, but I haven't seen it mentioned recently), it's worth a run through https://www.decisionproblem.com/paperclips/ . It's mostly humorous, but based on some very good thinking.
Building one paperclip could EASILY increase the median and average number of future paperclips more than investing one paperclip's worth of power into comet diversion.
Why do you think so? There will be no paperclips if planet and maximizer are destroyed.
Every bit of energy spent on paperclips is not spent on self-preservation. There are many threats (comets, aliens, black swans, etc.), caring about paperclips means not caring about them.
You might say maximizer will divide its energy among few priorities. Why is it rational to give less than 100% for self-preservation? All other priorities rely on this.