The font is a deliberate decision whether it's a bot or not, on which I have no firm opinion. A variety of accounts (how many different people are involved is anyone's guess) have chosen to set their output in monospace over the years here. I think of them like hipsters. Monospace is inferior for the majority of tasks (except arguably for programming, and for a few data processing tasks where the data is naturally columnar when represented with fixed character width) so they're making a decision to make you read their thoughts in an inferior fashion. You could of course override fixed width text but my recollection is that Slashdot uses the classic HTML for this purpose and not something you could conveniently override without affecting other text that you might not want to make monospace. However, I haven't looked at the CSS recently so you might have options there.
I handle it by simply not reading anything they write. As a speed reader I unfortunately sometimes read parts of their comments by accident, but otherwise I choose not to consume any of it. They want to make it harder to read? Fine, in that case I'll pass.