I can relate to some of this.
Consider and observe the structure of these three options:
- "What I mean is that ellipses overuse is annoying."
- "What I essentially mean is that ellipses overuse is annoying."
- "Ellipses overuse is annoying."
You are right that the last one would read as most confident. However, anything you post, you think. It is implied -- so safely omitted. The last option has the 'I think' section unsaid, but if you're reading it in a post someone made, it is a safe bet that they think that.
This means you can cut all the 'I think's (and variants of) from your posts without losing much, if anything. Of course, reader interpretation will matter too, and in some cases it can be worth stressing that it is merely your thoughts (I still often do it for feedback posts/reviews, but I used to do it a lot more).
Then it can end up being a tool for exaggeration instead of just white noise. If you're always saying that 'you think' something, it becomes filler text.
Oh, and if you don't think something, you can clarify that instead.
- "I heard that ellipses overuse is annoying."
As for ellipses use, I'm of the belief that they're strongest when used sparingly, since then they'll have more impact. If you use them a lot in your story, then this impact I perceive will quickly fade, and I'll be left with a more difficult story to read (comma's are less intrusive to my reading).
I'm happy enough to view it as a stylistic choice, but I'd probably mention it as a point of potential improvement.
Finally, overthinking posts/texts is a whole thing, but my advice would be to consider the stakes. Most often they are very low or even non-existent, in which case you ought to forgive yourself for making them imperfect.
That said, I still write up 'jokes' that I decide are unfunny and then . . . don't post/send. It's normal enough to think about what you post, after all (I think).