As with thin walls, particles are capable of moving faster than one pixel per frame, so it's not really a glitch that they can travel through very thin substances.
As with stickmen, it's been that way for a while. They might or might not get fixed in the future.
This mechanic is a part of the game and used in countless saves. Removing it would destroy too many saves to make it ever worth changing. Not at all a glitch, none of for SO LONG it's not even funny.
@Gamewizard71 Yes well, guess how many games of TPT's size have such accurate screen measurements that nothing glitches and falls through one pixel barriers.
Water goes through any solid that's 1px thick at diagonals, or if travelling quickly.
Derp -_-
For the love of pete, stop raging over the game's inconsistencies with your own wants and needs. Figure out how to deal with this, if you yell at us over stuff that's been established for years, you're not going to get any help at all.