I do have the same problem, but with HTML-comments like:

<!-- Kommentar -->

I would love to have this Bug fixed and see my comments again ;)

You can fix this with this workaround:

• go to the styles.css of the plugin. (vault/.obsidian/plugins/ultimate-todoist-sync)

Change this:
.cm-line:not(:hover):not(.cm-active) span.cm-comment { display: none; }
to this:
/* .cm-line:not(:hover):not(.cm-active) span.cm-comment { display: none; } */

What it does:

• The ID of the Todoist task is written down in %% %% Obsidians Comment syntax.
• The author does not want to see us the id, so he hides it.
• But ALL Comments are now hidden.
• The change above is commenting this feature out.
• Now you can see all your comments again. Even the ones in the todoist-Line, but that does not bother me.

👍 Thank you @MAWSpitau for this workaround.

🧐 I will try to build a CSS selector to only target/hide the Todoist comments.

I have a CSS rule handy to hide the start and end Obsidian comment surrounding the todoist_id.

.cm-line:not(:hover):not(.cm-active) > .cm-comment.cm-comment-start:has(~ .dataview.inline-field > .dataview.inline-field-key[data-dv-key="todoist_id"]),
.cm-line:not(:hover):not(.cm-active) > .cm-comment.cm-comment-start:has(~ .dataview.inline-field > .dataview.inline-field-key[data-dv-key="todoist_id"]) ~ .cm-comment.cm-comment-end
{
    display: none;
}

✅ This fixed the issue for me, it:

• hides the todoist_id start and end comment delimiters (%%) except when we hover over the line or edit the task.
• 🎉 does not hide other types of comments (I tested Java HTML and Ruby)

It is brittle because it depends on the CSS classes of the Tasks Obsidian plugin.

@MAWSpitau and anyone else interested, let me know if this works for you.

I also see this, so I like having a fix. Thank you!
I've tried the fix, and it does not hide the todoist_id, so I've elected to just comment out the comment hiding CSS from styles.css for the time being. Either way, I'm grateful to have my comments back, so thank you guys :)

Regarding the final fix, I know my preferences are just that, mine, but I thought I'd share them just in case they are useful.

• I would prefer it not to have more dependency on another tool, unless both projects are partnering (I've seen too many houses of cards come tumbling down because someone made a change, and these addons are becoming too important to my workflow)
• The todoist_ID should be hidden, and no other comments. I like my comments :)
• When on the line in edit mode, or mousing over the line, maybe todoist_id is visible

On a related note, I'm not sure if it's my mistake or some bug but I'm always able to see the todoist_id in edit mode, though the %% are hidden when not moused over or editing the line. I haven't had time to investigate this yet.