"rewrite their old content" I see what you did there. nice idea, thanks for sharing. More on reddit.com

For those that try it... If you don't like the result, click the Paraphrase button again for additional options. To OP... Of the three free "tones", you describe Casual as relaxed and informal, and Informal is described as relaxed and less formal. Both are noted as appropriate for communicating with friends. I see no difference in what i would be looking for from each. Since you are really only providing two tones for free, is there any way to evaluate the other tones for the quality of the rephrased outputs? More on reddit.com

look up pegasus it can be used for paraphrasing https://huggingface.co/tuner007/pegasus_paraphrase More on reddit.com

Half-jokingly: time and practice. Writing is a skill, and not an algorithmic one. There is no software substitute for being a good writer. The only way your writing will improve is through your attention to its improvement. Now, I know you asked for an affordable tool, and as grad students maybe time truly isn’t something we can afford. But practice is. Every time you do anything, write it down. Start with a paragraph about your work today. 6-9 months later you’ll have a dissertation and 150 paragraphs to sift through to see your improvement. More on reddit.com