Alfred

No need to guess! That’s exactly what happened. If you fill an unclosed curve which has start and end nodes that don’t coincide, you get this:

Join that curve to the other one (and, optionally, close it) to get the result you want.

You can marquee-select multiple nodes and then press the Delete key on your keyboard to delete the selected nodes in a single operation.

Thanks Walt !
As an aside though what a sorry state of the education systems that people don’t relate multiply by 0.8 exactly the same as 80%. 
As for other apps having better methods, I await the screen shots of equivalently comprehensive applications on the iPad for comparison. 

Can’t resist.  
 

Well, you can actually do trace with node tool, but only using a trick:
you can only add nodes on the curvature between two existing nodes. So create one node far away (using pen tool), then you can (switch to node tool and) add more nodes, and move them into correct position. I use this method often, starting with a rough outline, and then adding nodes for smaller details. And set fill opacity to 50% to see both background and curve on top.

I went to a jigsaw factory, by the time I got to the end I was in pieces, the tour guide told me to put myself together, I left the factory puzzled and felt a piece of me was missing. 

If anyone is interested in how jigsaws are made, and/or want more fascinating jigsaw-related facts, here’s a podcast episode which you might like: https://festivalofthespokennerd.com/podcast/series-2-episode-10-lock-and-key/
(The whole podcast set is a great listen if you like nerdy things.)

As Walt advised:
Simply typing @stokerg doesn’t have the desired effect. You don’t need to type the entire username, you just need to type enough of the name to make it appear on the list so that you can click on it.

For that you may need to move the node, or delete it.

Hasn’t Walt answered that question already?
 

Use the geometric subtract/add operations. First remove the half one, then copy/paste the remaining half to have another one, flip it horizontally, allign it accordingly and geometrical add both halfes to get one whole again.

screencast-batman.mp4  

I read a few of the little essays there. Not one word about legibility. In other words the author isn't interested in the reader's comprehension of the text. It seems that only the time spent by a typeface designer making a new font is worth considering.
Why do we set text? For readers, not the designers of typefaces, nor for programmers of applications that present text.
Use a monospaced font.

I think @kenmcd above answered to that question.
As for "thoughts" expressed in the referred link, it included the following wisdom, which basically states that form has no function:
"The abandon of proportional typesetting is a long awaited and necessary reform of the Latin alphabet and only the bourgeois tastes of the general public, who adore the oudated "beauty" of proportional typesetting, hinder the inevitable progress."
I have no words, but to me it seems that this writer only has characters and words, no thoughts. I am not sure under which rock they have lived but there are plenty of monospace types available in OpenType bourgeois misery (and earlier digital font technologies).
https://en.wikipedia.org/wiki/List_of_monospaced_typefaces

If this is just for an effect, you could use a spreadsheet app to split a character string to individual characters, copy paste the formula results as values and then copy paste transposed to rows (records), and then import the resulting source document into a Data Merge Layout grid. The amount of cells horizontally and vertically would determine the spacing and leading. 
a) In Excel:

b) In Publisher, using Data Merge Layout Tool in eight different ways (and orders the letters are fetched):
 

For details, refer the tutorial about make a calligraphy font bold here. Here I use Coreldraw, but still need to make the line segment by segment.
It is great if there is a tool that automatically generate the smooth transition like I propose.
https://www.designcontest.com/forum/tutorials/26210-corel-graphics-suite-coreldraw-corelphotopaint-tutorials.html/page-2

It can be a very very useful tool.....
Let say while the object is still in outline, if we make the corner rounded, the outline transition in thickness will automatically follow nicely. If we are creating a font family, we can automatically get the bold version by just shrinking the shape.
https://photos.app.goo.gl/42paF8cXMSik577P6

It should be an additional tool to set from this node to this node, you want this thickness. ...from that node to that node you can set it another line thickness. That is what I'm proposing here. I never find any app has this advantage. I'm not asking how to do that logo here....I'm giving an idea for Affinity designer developer for future development.
That is my logo. I designed that logo a long way. Segment by segment where the lines intersecting each other at corners at first.
For info, I'm Coreldraw, Affinity Designer, Inkscape and Adobe Illustrator user.

You were right on. When I went in and checked, I found that the Baseline Grid was turned on. I turned it off and that solved my problem.
Thank you very much for your advice.

The joins may not be clean with that approach...  of course, if the change is done at a segment level, there are limits to how effectively that can happen regardless.  Most apps set line thickness at the level of specific nodes added for the purpose, or possibly just at the nodes joining the segments.  The Affinity apps set it... arbitrarily along its length, totally ignoring the nodes and segments...

No. You cannot modify the character widths to be the same in any easy way.
Best to use an actual monospaced font.
If you want to modify a particular font to be monospaced... Monospacifier (https://github.com/cpitclaudel/monospacifier) is an option. But, not going to be as good as an actual monospace font.
Are you trying to use this together with a CJK font? (mono Latin characters are often available in CJK fonts)  There are utilities which would allow you to merge your custom mono font with another font.

You'd think it wouldn't be a big deal to be able to remember what you've already bought; but I've almost done the same thing myself several times! It's actually quite difficult to remember all the stuff you already have, especially if you don't use it regularly.
It would also be handy if it was easier to search your purchased items/downloads; it can be quite difficult scrolling up and down to check whether or not you already have any particular item.

@The_Snooze
Thanks for the suggestion. I'll pass it on to our website team.

In a proportional font, M is wider than average and i is narrower. Imposing a monospace look (e.g. by careful tracking and kerning) will result in large gaps between letters other than M and W, and especially huge gaps around narrow letters.

Now you use the Node Tool, do select all the bottom parts half nodes (as that hasn't much waves, you delete that one) and when you've selected all the bottom half's nodes press the delete key to get rid of all that bottom part half!
Or just reuse the wavy yellow curve part from here, resize and color it to your needs ...

screencast4.mp4
Here's the ADe file again ...
wysiwyg_parts.afdesign

That title is about deleting a node whilst tracing. (When It’s not complete)
 
This is about deleting a node after tracing.
 
But I found the answer of this one.
 
Thank you very much all for the answers.