Seven months ago I posted A Case Against Strong Longtermism on the forum, and it caused a bit of a stir. I promised to respond to all the unaddressed comments, and as a result, have produced a four-part "sequence" of sorts.
The first and last post, A Case Against Strong Longtermism and The Poverty of Longtermism deal with longtermism specifically, while the middle two posts Proving Too Much and The Credence Assumption deal with bayesian epistemology, the iceberg-like structure keeping longtermism afloat.
The subsections are listed below and don't need to be read in any particular order. Special thanks to Max Daniel, Jack Malte, Elliott Hornley, Owen Cotton Barratt, and Mauricio in particular, without whose criticism this sequence would not exist.
Now time to move on to other subjects...
You can imagine that OP has limited opportunities or interest or time to improve, and can only focus on one thing. In that case I'd strongly encourage focusing on higher quality arguments over better style, as I usually find the lack of the former much more offputting than the latter.