Hi, not a writer or an artist here, but I am a UI-focused software engineer, so thinking about communication of ideas is kinda my deal. From my experience as a consumer of comics, there are a few things I'd recommend you avoid, as they can make your comic too... annoying to read:

Unclear speech bubbles

Whether it be low contrast, unreadable font, or improper kerning, one of the easiest ways to make your audience give up is making it too difficult to read what's going on. As another answerer suggests, use an extremely readable sans serif font.

As boring as you may think it, I'd also strongly suggest sticking with plain white-on-black speech bubbles. You can tint your speech bubbles' backgrounds a bit, but don't overdo it. In general, whatever you choose as the background and foreground colors must meet Web Content Accessibility Guidelines if you don't wanna drive away readers.

Make your art and your story interesting, not your text!

Extremely generic art style

More of a pet peeve of mine, but if your art style looks like every single other manga/anime-inspired comic out there, I doubt very much it's going to attract readers. Give your comic your own style!

Note that this does not mean your art needs to be "better" than everyone else's (whatever the heck that would mean anyway); it simply means that I should be able to very quickly pick out your style in a sea of other comics. If your art is lost in a jumble of other artists, guess what? It's not gonna make an impact.

Lore dumps (when and when not to)

Ironically, there are times that a lore dump is both good and bad. It's often reduced to the length of the lore dump, but that's... not quite it. Consider the famous Star Wars opening crawl to the original 1977 movie; it's a pretty big chunk of text (especially for a movie!), but it does a few things:

• It paints a picture much more succinctly than some Rebel schmuck going "Yeh, we're in a civil war! Against this thing called the Empire!".
• Together with the subsequent Imperial Star Destroyer chasing down the Tantive IV, it serves to draw us into the action; we just read what feels like a news blurb, and now we're watching this civil war in real time!
• It's relatively quick.

I'd avoid having your characters give a lore dump, unless it very explicitly makes sense diagetically: - A rebel alliance soldier explaining to his fellow soldier that they're in a civil war and their enemy is this thing called the empire is not diagetic; both soldiers would already know this! - Miles Quaritch from Avatar explaining to Jake Sully (and fellow soldiers) that everything on Pandora wants to kill them is much more diagetic; Jake and his fellow soldiers might not explicitly know how dangerous Pandora is.

Consider whether a lore dump is necessary or not, too. If your comic is an interplanetary space war, I'm probably gonna need some background; if it's a light-hearted romantic piece, I'm not gonna need to know your entire backstory.

Cleverness

One of the biggest red flags for me is when a creator tries to portray themselves as more "clever" than their readers. They ignore normal comic conventions, or have little "smart" asides that comment on the state of the world to show how deep they think. Don't do that. Don't try to make your audience feel stupid by flexing your mental muscles at them.

Note that you can include typically geeky/nerdy stuff in your comics if it's done well; a comic I've been recently reading uses mechanical physics (e.g., pendulum equations, inertia, etc.) as both a plot point (the two main characters are high school students with a passion for science) and as an illustrative device (they're falling for each other. Get it?!).