Although my site seems to be responsive (not necessarily how’d I’d like it, but from my understanding it cannot be changed. It is either responsive, or not.), the post titles are not displaying properly on mobile.
Your h1 has line-height:0em. This can cause issues on posts with long titles that will require it to use a second line or on mobile(where most titles also use second line).
Setting h1‘s line-height to at least 1em should fix the issue.